mMainComponentName Keep in line with above in ReactActivityDelegate (#…

…32685)

Summary:
```
public String getMainComponentName() {
    return mMainComponentName;
}

protected void onCreate(Bundle savedInstanceState) {
    String mainComponentName = getMainComponentName();
    mReactDelegate =
        new ReactDelegate(
            getPlainActivity(), getReactNativeHost(), mainComponentName, getLaunchOptions()) {
          Override
          protected ReactRootView createRootView() {
            return ReactActivityDelegate.this.createRootView();
          }
        };
    // mMainComponentName rename is mainComponentName
    if (mainComponentName != null) {
      loadApp(mainComponentName);
    }
  }
```

## Changelog

<!-- Help reviewers and the release process by writing your own changelog entry. For an example, see:
https://github.com/facebook/react-native/wiki/Changelog
-->

[CATEGORY] [TYPE] - Message

Pull Request resolved: #32685

Reviewed By: ShikaSD

Differential Revision: D32754475

Pulled By: cortinico

fbshipit-source-id: 46c395a5d6c6508c14eaa163a1e824f0c3cb8b80

ReactAndroid/src/main/java/com/facebook/react/ReactActivityDelegate.java

@@ -82,7 +82,7 @@ protected ReactRootView createRootView() {
             return ReactActivityDelegate.this.createRootView();
           }
         };
-    if (mMainComponentName != null) {
+    if (mainComponentName != null) {
       loadApp(mainComponentName);
     }
   }