Build with new grpc release

[HannahShiSFB]

@wu-hui
I tried various configuration combinations, turned out the following change would fix the build, can you verify it?

diff --git a/Podfile b/Podfile
index eeed2ac..4be00d5 100644
--- a/Podfile
+++ b/Podfile
@@ -1,11 +1,13 @@
 source 'https://github.com/CocoaPods/Specs.git'

-use_frameworks!
+use_modular_headers!

 platform :ios, '11.0'
 inhibit_all_warnings!

 target 'NewSwiftApp' do
+  pod 'gRPC', '~> 1.57.0'
+  pod 'gRPC-Core', '~> 1.57.0'
   pod 'gRPC-C++', '~> 1.57.0'
 end