Remove keychain entries if fresh install #938

Job	Run time
spm-build-test (macos-15, iphonesimulator)	3m 8s
pod-lib-lint (macos-15, GoogleSignInSwiftSupport.podspec)	9m 5s
pod-lib-lint (macos-15, GoogleSignIn.podspec)	7m 59s
pod-lib-lint (macos-15, GoogleSignIn.podspec, --use-static-frameworks)	5m 20s
pod-lib-lint (macos-15, GoogleSignInSwiftSupport.podspec, --use-static-frameworks)	7m 38s
spm-build-test (macos-15, macosx)	1m 27s
	34m 37s

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