storage(feat): adding support for Workload identity

[shubhangi-google]

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closes: #<issue_number_goes_here>

[snippet-bot]

Here is the summary of changes.

You are about to add 1 region tag.

• google-cloud-storage/samples/storage_generate_signed_url_v4_workload_identity.rb:15, tag storage_generate_signed_url_v4_workload_identity

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