title: Flutter remove border expansion tile
body: <p>i created an expansion tile and i cannot find a way how to remove the border or shadow of the box. Do you guys know the command?</p>
  <p>here is a picture</p>
  <p><a href="https://gyazo.com/6dc133ca91071c0afeb65899688311aa" rel="noreferrer">https://gyazo.com/6dc133ca91071c0afeb65899688311aa</a></p>
  <p>here is a picture, you can see it on the corner edge
  sorry because it is long but this is the full expansion</p>
  <pre><code>ExpansionTile(
  trailing: Text(''),
  leading: Container(
      margin: new EdgeInsets.only(left: 0, top: 10.0, right: 0.0, bottom: 0.0),
      child: Image.asset(
          'images/food.png'
      )),
  title: Row(
      children: &lt; Widget &gt; [
  
  
          Padding(
              padding: const EdgeInsets.only(right: 0, left: 10, top: 15, bottom: 15),
                  child: Column(textDirection: TextDirection.ltr, crossAxisAlignment: CrossAxisAlignment.start, children: &lt; Widget &gt; [
  
  
  
                      Container(
                          margin: new EdgeInsets.only(left: 0.0, top: 7.0, right: 0.0, bottom: 3.0),
                          child: Text(
                              'Food System', textAlign: TextAlign.left,
                              style: TextStyle(
                                  color: Colors.white,
                                  fontSize: 25,
                              ),
                          )),
                      Text(
                          'Customize the food system', textAlign: TextAlign.left,
                          style: TextStyle(
  
                              color: Colors.white,
                              fontSize: 15,
                          ),
                      )
  
                  ])),
  
      ], ),
  children: &lt; Widget &gt; [
  
  
  
      Container(
          width: 300,
          margin: new EdgeInsets.only(left: 10.0, top: 0.0, right: 10.0, bottom: 10.0),
          color: Colors.transparent,
          child: new Container(
  
  
              padding: new EdgeInsets.all(20),
              child: Column(crossAxisAlignment: CrossAxisAlignment.start, children: &lt; Widget &gt; [
                  Container(
                      margin: new EdgeInsets.only(left: 15.0, top: .0, right: 20.0, bottom: 5.0),
                      child: Text('Storage', style: TextStyle(color: Colors.white, fontSize: 20, fontWeight: FontWeight.bold)), ),
                  Center(child: Column(children: &lt; Widget &gt; [
                      Container(
                          child: Column(children: &lt; Widget &gt; [
                              Text('2.4 KG left        -        7 Days', style: TextStyle(color: Colors.white, fontSize: 20)),
                              Text('200 G / Meal  - 600 G / Day', style: TextStyle(color: Colors.white, fontSize: 20)),
                          ], ),
                          margin: new EdgeInsets.only(left: 0, top: 0, right: 0, bottom: 10.0),
                      )
  
                  ], )),
                  Container(
                      margin: new EdgeInsets.only(left: 18.0, top: .0, right: 20.0, bottom: 5.0),
                      child: Text('Meal times', style: TextStyle(color: Colors.white, fontSize: 20, fontWeight: FontWeight.bold)), ),
                  Center(child: Column(children: &lt; Widget &gt; [
  
                      Text('1.   Breakfast   -   8:30 AM', style: TextStyle(color: Colors.white, fontSize: 20)),
                      Text('2.   Lunch         -   2:00 PM', style: TextStyle(color: Colors.white, fontSize: 20)),
                      Text('3.   Dinner        -   9:15  PM', style: TextStyle(color: Colors.white, fontSize: 20)),
                  ], ))
              ], ), )
      ),
  
  
  
  
      Container(
          height: 50.0,
          width: 300,
  
          margin: new EdgeInsets.only(left: 10.0, top: 10.0, right: 10.0, bottom: 10.0),
          color: Colors.transparent,
          child: new Container(
              decoration: new BoxDecoration(
                  color: Colors.blue,
                  gradient: LinearGradient(
                      begin: Alignment.topRight,
                      end: Alignment.bottomLeft,
                      colors: [Color(0xff37b9ff), Color(0xff5d3afd)]),
                  borderRadius: new BorderRadius.only(
                      topLeft: const Radius.circular(40.0),
                          topRight: const Radius.circular(40.0),
                              bottomLeft: const Radius.circular(40.0),
                                  bottomRight: const Radius.circular(40.0),
  
                  )
              ),
              child: Center(child:
  
                  Text('Edit', style: TextStyle(color: Colors.white, fontSize: 15))
  
                  , )
          )
      ),
  ])
  </code></pre>