Fix errors in tutorial so it will build and run

[claresudbery]

!! Anyone using this will need to put their application ID in FriendlyChatSwift/info.plist - currently line 63 !! Also I commented out some code related to GIDSignIn - this will need fixing in to bring in line with latest GIDSigIn code. Migration guide here: https://developers.google.com/identity/sign-in/ios/quick-migration-guide

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