doc: format and ran prettier on precommit.md
doc: format and ran prettier on precommit.md

Change-Id: Ibcff373bc817f2b67abbb45b85ae7ccb34b5bcfd
Reviewed-on: https://team-review.git.corp.google.com/c/golang/discovery/+/768318
CI-Result: Cloud Build <ea5729d4cf3392b9d382b6ca272c65aa27554f44@system.gserviceaccount.com>
Reviewed-by: Jonathan Amsterdam <e3d3698b2ccd5955e4adf250d0785062d0f9018b@google.com>

golang/pkgsite,golang/pkgsite,golang/pkgsite,golang/pkgsite