Use `getDefaultCliVersion` for `start-proxy` #7038

Job	Run time
Ruby analysis (macos-latest, nightly-latest)	1m 13s
Ruby analysis (ubuntu-latest, nightly-latest)	48s
Ruby analysis (ubuntu-latest, default)	50s
Ruby analysis (macos-latest, default)	1m 10s
Ruby analysis (macos-latest, linked)	56s
Ruby analysis (ubuntu-latest, linked)	58s
	5m 55s

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