Remove ContentSizeChangeEvent from core

Summary:
This class is not referenced anywhere. It used to be part of webview, which has been removed from RN's core.

Since we still have [external users](https://github.com/expo/expo/blob/923016204c239cdad07b89626ac65eb505623d98/android/expoview/src/main/java/versioned/host/exp/exponent/modules/api/components/webview/RNCWebView.java#L133) of this class, let's deprecate it first.

Changelog: [Android][Removed] Deprecated internal ContentSizeChangeEvent

Reviewed By: NickGerleman

Differential Revision: D50325736

fbshipit-source-id: 5e1005b92764ae08bcc10607f675b3311b3e2ddb

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/uimanager/events/ContentSizeChangeEvent.java

@@ -11,7 +11,12 @@
 import com.facebook.react.bridge.WritableMap;
 import com.facebook.react.uimanager.PixelUtil;
 
-/** Event dispatched when total width or height of a view's children changes */
+/**
+ * Event dispatched when total width or height of a view's children changes.
+ *
+ * @deprecated Please define your own event for custom components
+ */
+@Deprecated
 public class ContentSizeChangeEvent extends Event<ContentSizeChangeEvent> {
 
   public static final String EVENT_NAME = "topContentSizeChange";