Fix spelling and logic for Gitaly hook volumes

What does this MR do?

Closes #2512 (closed)

Reimplementation of !1742 (closed):

• Sets the correct target branch to master
• Replaces has with hasKey
• Slightly renames volumes
• Catches another 'receive' misspelling in the docs

Checklist

See Definition of done.

For anything in this list which will not be completed, please provide a reason in the MR discussion.

Required

• Merge Request Title and Description are up to date, accurate, and descriptive
• MR targeting the appropriate branch
• MR has a green pipeline on GitLab.com

Expected (please provide an explanation if not completing)

• Test plan indicating conditions for success has been posted and passes
• Documentation created/updated
• Tests added
• Integration tests added to GitLab QA
• Equivalent MR/issue for omnibus-gitlab opened

Closes #1742 (closed)