Fix a binary name for gh-action in usage

[Kuniwak]

Before

$ gh-action --help
usage: unity-meta-check-gh-action -inputs-json <json>
  -inputs-json string
        JSON string of "inputs" context value of GitHub Actions
  -version
        print version

After

$ gh-action --help
usage: gh-action -inputs-json <json>
  -inputs-json string
        JSON string of "inputs" context value of GitHub Actions
  -version
        print version

Acknowledgment

ReportedBy: @ponkio-o

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[ponkio-o]

LGTM!