android deps: Finish removal of react-native-orientation.

In 0d5a19a, for zulip#4147, we forgot to remove some Android
configuration specific to `react-native-orientation` in
MainActivity.java [1], added in 3149c9d. So, remove it.

It appears that the iOS configuration at the
`react-native-orientation` doc was never done, so there's nothing to
do for that.

Greg pointed out that this override was replicated in
ReceiveShareActivity.kt when that file was created (in 0b84717)
and that he was puzzled by it while reviewing zulip#4124 and supposed it
might be generic RN boilerplate. Now that we've identified it,
remove it.

[1]: https://github.com/yamill/react-native-orientation#configuration

android/app/src/main/java/com/zulipmobile/MainActivity.java

@@ -1,7 +1,5 @@
 package com.zulipmobile;
 
-import android.content.Intent;
-import android.content.res.Configuration;
 import android.os.Bundle;
 import android.webkit.WebView;
 import com.facebook.react.ReactActivity;
@@ -22,12 +20,4 @@ protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         WebView.setWebContentsDebuggingEnabled(true);
     }
-
-    @Override
-    public void onConfigurationChanged(Configuration newConfig) {
-        super.onConfigurationChanged(newConfig);
-        Intent intent = new Intent("onConfigurationChanged");
-        intent.putExtra("newConfig", newConfig);
-        this.sendBroadcast(intent);
-    }
 }

android/app/src/main/java/com/zulipmobile/sharing/ReceiveShareActivity.kt

@@ -2,7 +2,6 @@ package com.zulipmobile.sharing
 
 import android.content.Context
 import android.content.Intent
-import android.content.res.Configuration
 import android.net.Uri
 import android.os.Bundle
 import android.util.Log
@@ -105,13 +104,6 @@ class ReceiveShareActivity : ReactActivity() {
         }
         return params
     }
-
-    override fun onConfigurationChanged(newConfig: Configuration) {
-        super.onConfigurationChanged(newConfig)
-        val intent = Intent("onConfigurationChanged")
-        intent.putExtra("newConfig", newConfig)
-        this.sendBroadcast(intent)
-    }
 }
 
 class ShareParamsParseException(errorMessage: String) : RuntimeException(errorMessage)