Upgrade GoogleTest to 1.10.0 (#4250)

Firestore/Example/GoogleTest.podspec

@@ -17,7 +17,7 @@
 
 Pod::Spec.new do |s|
   s.name             = 'GoogleTest'
-  s.version          = '1.8.1'
+  s.version          = '1.10.0'
   s.summary          = 'Google Test'
 
   s.description      = <<-DESC
@@ -86,6 +86,8 @@ Google's C++ test framework.
       '"${PODS_ROOT}/GoogleTest/googletest"'
   }
 
+  s.compiler_flags = '$(inherited) -Wno-comma'
+
   s.prepare_command = <<-'CMD'
     # Remove includes of files in internal/custom
     sed -i.bak -e '/include.*internal\/custom/ d' \