message: Fix parameter type in example document
diff: </scale>
  <noise2d name="n9" type="color3">
  <input name="texcoord" type="vector2" nodename="s1"/>
  - <parameter name="amplitude" type="color3" value="0.03,0.04,0.06" publicname="grain_gain"/>
  + <parameter name="amplitude" type="vector3" value="0.03,0.04,0.06" publicname="grain_gain"/>
  </noise2d>
  <inside name="n10" type="color3">
  <input name="mask" type="float" nodename="img4"/>
  