FIAM bump podspec version to 0.19.3 (#5386)

Firebase.podspec

@@ -101,7 +101,7 @@ Simplify your app development, grow your user base, and monetize more effectivel
 
   s.subspec 'InAppMessaging' do |ss|
     ss.dependency 'Firebase/CoreOnly'
-    ss.ios.dependency 'FirebaseInAppMessaging', '~> 0.19.2'
+    ss.ios.dependency 'FirebaseInAppMessaging', '~> 0.19.3'
     ss.ios.deployment_target = '9.0'
   end
 

FirebaseInAppMessaging.podspec

@@ -1,6 +1,6 @@
 Pod::Spec.new do |s|
   s.name             = 'FirebaseInAppMessaging'
-  s.version          = '0.19.2'
+  s.version          = '0.19.3'
   s.summary          = 'Firebase In-App Messaging for iOS'
 
   s.description      = <<-DESC