docs(app, ios): update docs to reflect 11.5.0 firebase-ios-sdk version

missed this during the SDK update

Author: mikehardy

docs/index.md

@@ -305,7 +305,7 @@ Open your projects `/ios/Podfile` and add any of the globals shown below to the
 
 ```ruby
 # Override Firebase SDK Version
-$FirebaseSDKVersion = '11.4.0'
+$FirebaseSDKVersion = '11.5.0'
 ```
 
 Once changed, reinstall your projects pods via pod install and rebuild your project with `npx react-native run-ios`.