[google_maps_flutter] Mark iOS arm64 simulators as unsupported

[jmagman]

Before flutter/flutter#87244, any app using the google_maps_flutter plugin would not build on an M1 Mac.

Replace deprecated 'VALID_ARCHS[sdk=iphonesimulator*]' => 'x86_64' with 'EXCLUDED_ARCHS[sdk=iphonesimulator*]' => 'arm64'.

Fixes flutter/flutter#87242
See also #4208

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[jmagman]

Test failure to be fixed in flutter/flutter: flutter/flutter#87362

[stuartmorgan-g]

LGTM with version nit.

[fluttergithubbot]

This pull request is not suitable for automatic merging in its current state.

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