title: Remove seaborn lineplot legend title
body: <p>I would like to remove the title from my seaborn lineplot legend. I tried using <a href="https://stackoverflow.com/a/45335602/2970186">this answer</a> to no avail:</p>
  
  <pre><code>import matplotlib.pyplot as plt
  import seaborn as sns; sns.set()
  fmri = sns.load_dataset("fmri")
  fig, ax = plt.subplots()
  g = sns.lineplot(x="timepoint", y="signal", hue="event", data=fmri, ax=ax)
  ax.legend().set_title('')
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/V18FL.png" rel="noreferrer"><img src="https://i.stack.imgur.com/V18FL.png" alt="Seaborn lineplot still with &#39;event&#39; title"></a></p>
  
  <p>I get the same if I try to set the title to <code>None</code>. Interestingly, setting the title to something else seems to prepend to the existing title:</p>
  
  <pre><code>ax.legend().set_title('Something else')
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/HJnH0.png" rel="noreferrer"><img src="https://i.stack.imgur.com/HJnH0.png" alt="Seaborn lineplot still with prepend title"></a></p>
  
  <p>It almost looks like seaborn is treating the title as a hidden legend entry. How can I resolve this?</p>