Bump GoogleUtilities version 6.2.2 (#3331)

* Bump GoogleUtilities version 6.2.2

* Changelog updates 6.2.2

Author: maksymmalyhin

GoogleUtilities.podspec

@@ -1,6 +1,6 @@
 Pod::Spec.new do |s|
   s.name             = 'GoogleUtilities'
-  s.version          = '6.2.1'
+  s.version          = '6.2.2'
   s.summary          = 'Google Utilities for iOS (plus community support for macOS and tvOS)'
 
   s.description      = <<-DESC

GoogleUtilities/CHANGELOG.md

@@ -1,5 +1,8 @@
-# Unreleased
+# 6.2.2
 - Add explicit Foundation import for headers.
+- Fix headers import. (#3277)
+- Fix README. (#3305)
+- Fix `GULMutableDictionary` thread-safety. (#3322)
 
 # 6.2.1
 - Fix Xcode 11 build warning. (#3133)