Fastlane: Update Xcode version requirement in Fastfile.
Fastlane: Update Xcode version requirement in Fastfile.

vector-im/riot-ios,vector-im/vector-ios,vector-im/riot-ios,vector-im/riot-ios,vector-im/riot-ios,vector-im/riot-ios,vector-im/riot-ios,vector-im/vector-ios,vector-im/vector-ios