Remove support for Android API < 23 in ReactFragment (facebook#39668)

Summary:
Pull Request resolved: facebook#39668

Since minsdk version was increased to 23, we are deleting code using Android APIs < 23 for class ReactFragment

chnagelog: [Android][Breaking] Remove support for Android API < 23 in ReactFragment

Reviewed By: NickGerleman

Differential Revision: D48545506

fbshipit-source-id: 2f267ab73b9560455ebb64cfb824c583927d315f

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/ReactFragment.java

@@ -7,10 +7,8 @@
 
 package com.facebook.react;
 
-import android.annotation.TargetApi;
 import android.app.Activity;
 import android.content.Intent;
-import android.os.Build;
 import android.os.Bundle;
 import android.view.KeyEvent;
 import android.view.LayoutInflater;
@@ -161,13 +159,11 @@ public int checkPermission(String permission, int pid, int uid) {
     return getActivity().checkPermission(permission, pid, uid);
   }
 
-  @TargetApi(Build.VERSION_CODES.M)
   @Override
   public int checkSelfPermission(String permission) {
     return getActivity().checkSelfPermission(permission);
   }
 
-  @TargetApi(Build.VERSION_CODES.M)
   @Override
   public void requestPermissions(
       String[] permissions, int requestCode, PermissionListener listener) {