experimental/documentation/gerrit.md: fix error

NOTRY=true
Change-Id: I40762016f28cd5814c79e4159fa4f73d585f6545
Reviewed-on: https://skia-review.googlesource.com/21377
Reviewed-by: Hal Canary <halcanary@google.com>
Commit-Queue: Hal Canary <halcanary@google.com>
1 file changed