Turn off CLANG_WARN_QUOTED_INCLUDE_IN_FRAMEWORK_HEADER in CocoaPod targets - #68817

Description

CocoaPods 1.10 does this as of CocoaPods/CocoaPods#9902 to avoid warnings and errors in Xcode 12. Duplicate the behavior in Flutter for users on older versions (minimum required is 1.6, 1.8 is recommended).

This warning plays poorly with pods that also opt into treating warnings as errors, which causes compilation failures, not just warnings:
https://github.com/CocoaPods/Specs/blob/master/Specs/b/c/f/GoogleDataTransportCCTSupport/3.2.0/GoogleDataTransportCCTSupport.podspec.json#L56

Related Issues

Fixes #68813

Tests

I'm not sure how to test this, but I reproduced the compilation failure locally, and confirmed it no longer produces errors or warnings related to quoted includes.

1. Downgrade from 1.10.

sudo gem uninstall cocoapods
sudo gem install cocoapods -v 1.9.3

2. Add any Flutter plugin to a project to produce the ios/Podfile, then to that add GoogleDataTransportCCTSupport

target 'Runner' do
  use_frameworks!
  use_modular_headers!

  pod 'GoogleDataTransportCCTSupport', '3.2.0'
...

3. cd ios && pod install
4. Open ios/Runner.xcworkspace in Xcode 12 and turn on "Quoted Include in Framework Header" build setting in the Pods target or run the "Update build settings" migrator thing.
5. flutter build ios fails

                      In file included from <module-includes>:1:
                      ios/Pods/Target Support Files/nanopb/nanopb-umbrella.h:13:9: error: double-quoted include "pb.h" in framework header, expected angle-bracketed instead
                      [-Werror,-Wquoted-include-in-framework-header]
                      #import "pb.h"
                              ^~~~~~
                              <pb.h>

Apply this patch, no more failures.