Simplify capture invalidation

Remove the unnecessary requestInvalidate() indirection. Use a single
invalidate() method instead.

server/src/main/java/com/genymobile/scrcpy/video/ScreenCapture.java

@@ -211,9 +211,4 @@ public class ScreenCapture extends SurfaceCapture {
             SurfaceControl.closeTransaction();
         }
     }
-
-    @Override
-    public void requestInvalidate() {
-        invalidate();
-    }
 }