update docs/api/media/video-context.md.

fix:
调整
~~~
<video id="myVideo" src="https://bjetxgzv.cdn.bspapp.com/VKCEYUGU-uni-app-doc/360e4b20-4f4b-11eb-8a36-ebb87efcf8c0.mp4" @error="videoErrorCallback" :danmu-list="danmuList"
				    enable-danmu danmu-btn controls></video>
~~~
为
~~~
<video id="myVideo" src="https://bjetxgzv.cdn.bspapp.com/VKCEYUGU-uni-app-doc/360e4b20-4f4b-11eb-8a36-ebb87efcf8c0.mp4" @error="videoErrorCallback" :danmu-list="danmuList"
				    enable-danmu danmu-btn controls>
</video>
~~~

docs/api/media/video-context.md

@@ -33,7 +33,8 @@
 		<view class="page-body">
 			<view class="page-section">
 				<video id="myVideo" src="https://bjetxgzv.cdn.bspapp.com/VKCEYUGU-uni-app-doc/360e4b20-4f4b-11eb-8a36-ebb87efcf8c0.mp4" @error="videoErrorCallback" :danmu-list="danmuList"
-				    enable-danmu danmu-btn controls></video>
+				    enable-danmu danmu-btn controls>
+                                </video>
 
 				<view class="uni-list">
 					<view class="uni-list-cell">