Remove keychain entries if fresh install #936

Job	Run time
spm-build-test (macos-15, iphonesimulator)	4m 31s
spm-build-test (macos-15, macosx)	2m 39s
pod-lib-lint (macos-15, GoogleSignInSwiftSupport.podspec, --use-static-frameworks)	6m 23s
pod-lib-lint (macos-15, GoogleSignInSwiftSupport.podspec)	8m 21s
pod-lib-lint (macos-15, GoogleSignIn.podspec)	7m 38s
pod-lib-lint (macos-15, GoogleSignIn.podspec, --use-static-frameworks)	6m 35s
	36m 7s

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