config-gerrit: update repo download config options
config-gerrit: update repo download config options

This was renamed to just "repo" a while ago but the docs were missed.

Change-Id: I1dea13213e0c174c076a7ca47153abb406fa5db8

GerritCodeReview/gerrit,GerritCodeReview/gerrit,GerritCodeReview/gerrit,GerritCodeReview/gerrit,GerritCodeReview/gerrit,GerritCodeReview/gerrit,GerritCodeReview/gerrit,GerritCodeReview/gerrit