ios [nfc]: Remove Facebook copyright notices from some files.

Part of the RN v0.61 -> v0.62 changes to the template app [1],
corresponding to facebook/react-native@6a10d5dfd. This can freely be
done before the main upgrade commit, obviously.

[1] https://react-native-community.github.io/upgrade-helper/?from=0.61.5&to=0.62.2

ios/ZulipMobile.xcodeproj/project.pbxproj

@@ -176,7 +176,6 @@
 			isa = PBXProject;
 			attributes = {
 				LastUpgradeCheck = 940;
-				ORGANIZATIONNAME = Facebook;
 				TargetAttributes = {
 					13B07F861A680F5B00A75B9A = {
 						DevelopmentTeam = 66KHCWMEYB;

ios/ZulipMobile/AppDelegate.h

@@ -1,12 +1,3 @@
-/**
- * Copyright (c) Facebook, Inc. and its affiliates.
- * All rights reserved.
- *
- * This source code is licensed under the BSD-style license found in the
- * LICENSE file in the root directory of this source tree. An additional grant
- * of patent rights can be found in the PATENTS file in the same directory.
- */
-
 #import <React/RCTBridgeDelegate.h>
 #import <UIKit/UIKit.h>
 #import <UMReactNativeAdapter/UMModuleRegistryAdapter.h>

ios/ZulipMobile/AppDelegate.m

@@ -1,12 +1,3 @@
-/**
- * Copyright (c) Facebook, Inc. and its affiliates.
- * All rights reserved.
- *
- * This source code is licensed under the BSD-style license found in the
- * LICENSE file in the root directory of this source tree. An additional grant
- * of patent rights can be found in the PATENTS file in the same directory.
- */
-
 #import "AppDelegate.h"
 
 #import <React/RCTBridge.h>

ios/ZulipMobile/main.m

@@ -1,12 +1,3 @@
-/**
- * Copyright (c) Facebook, Inc. and its affiliates.
- * All rights reserved.
- *
- * This source code is licensed under the BSD-style license found in the
- * LICENSE file in the root directory of this source tree. An additional grant
- * of patent rights can be found in the PATENTS file in the same directory.
- */
-
 #import <UIKit/UIKit.h>
 
 #import "AppDelegate.h"