Depend on GSI 7.1.0 in GoogleSignSwiftSupport.podspec

[mdmathias]

This change makes it so that GoogleSignInSwiftSupport.podspec depends upon v7.1.0 (and up) on CocoaPods instead of "7.1.0-fac-beta-1.1.0". This helps to avoid needing to release a new version of GoogleSignInSwiftSupport on CocoaPods, which would be required if we changed GoogleSignInSwiftSupport's GSI dependency version.

SKIP_INTEGRATION_TESTS=YES

[mdmathias]

GoogleSignInSwiftSupport.podspec fails to lint because that podspec lists its dependency on GSI as s.dependency 'GoogleSignIn', '~> 7.1'. Yet, the lint command is

pod lib lint GoogleSignInSwiftSupport.podspec --verbose --no-clean \
     --sources=https://cdn.cocoapods.org/ \
     --include-podspecs='GoogleSignIn.podspec'

This will try to use the local GoogleSignIn.podspec for the Swift Support's podspec dependency. GSI's version in the local podspec is '7.1.0-fac-beta-1.1.0'. Thus, the linting fails with the error:

-> GoogleSignInSwiftSupport (7.1.0)
    - ERROR | [iOS] unknown: Encountered an unknown error (CocoaPods could not find compatible versions for pod "GoogleSignIn":
  In Podfile:
    GoogleSignIn (from `.`)

Essentially, the lint command is saying to use the local GoogleSignIn.podspec to satisfy GoogleSignInSwiftSupport.podspec's dependency on GSI, but the linting fails because the versions do not match.

If I remove using the local GoogleSignIn.podspec from the lint command, then linting will use GSI v7.1.0 (published on cocoapods.org) to satisfy GoogleSignInSwiftSupport.podspec's dependency. The command below passes locally:

pod lib lint GoogleSignInSwiftSupport.podspec --verbose \
     --sources=https://cdn.cocoapods.org

Thus, I think this is fine to merge as is. We want GoogleSignInSwiftSupport.podspec to depend upon GSI v7.1.0 to avoid making a new release for the Swift Support pod. Additionally, "7.1.0-fac-beta-1.1.0" will be a published version of GSI upon release. This means future pod lib lints won't fail.

[mdmathias]

Actually, I've changed my mind! Disregard most of #399 (comment) in favor of #400.