Docs: Fixed git commands

Suzanne Selhornrequested to merge
docs-selhorn-sharedinstall into master

What does this MR do?

This fixes a few incorrect git commands in this topic: https://docs.gitlab.com/runner/install/osx.html#limitations-on-macos

Closes: !2225 (closed)

Edited by 🤖 GitLab Bot 🤖

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