canvas: 移除一些临时样式写法，放开AnimationFrame

pages/component/canvas/canvas-context.uvue

@@ -851,17 +851,10 @@
 <style>
   .page {
     flex: 1;
-    overflow: hidden;
-    /* #ifdef MP-WEIXIN */
-    height: 100vh;
-    /* #endif */
   }
 
   .scroll-view {
     flex: 1;
-    /* #ifdef MP-WEIXIN */
-    overflow: hidden;
-    /* #endif */
   }
 
   .canvas-element {

pages/component/canvas/canvas.uvue

@@ -15,10 +15,8 @@
       </view>
       <button @click="onCreateImage">createImage</button>
       <button @click="onCreatePath2D">createPath2D</button>
-      <!-- #ifndef MP -->
       <button @click="startAnimationFrame">requestAnimationFrame</button>
       <button @click="stopAnimationFrame">cancelAnimationFrame</button>
-      <!-- #endif -->
       <view style="padding: 8px 10px;">CanvasContext API 演示</view>
       <navigator url="./canvas-context">
         <button>CanvasContext API</button>