Update version for 5.2.2 release

Change-Id: I15064a1a731c00ddc928d6eee9520bd0e2b5a3ee

Author: morganchen12

FirebaseUI.podspec

@@ -1,6 +1,6 @@
 Pod::Spec.new do |s|
  s.name = 'FirebaseUI'
- s.version = '5.2.1'
+ s.version = '5.2.2'
  s.summary = 'UI binding libraries for Firebase.'
  s.homepage = 'https://github.com/firebase/FirebaseUI-iOS'
  s.license = { :type => 'Apache 2.0', :file => 'LICENSE' }