Clarify how to update the docs branch in the RELEASE-CHECKLIST with concrete instructions

Docker-DCO-1.1-Signed-off-by: Andrew Page <admwiggin@gmail.com> (github: tianon)

hack/RELEASE-CHECKLIST.md

@@ -175,19 +175,23 @@ release is uploaded to get.docker.io!
 
 ### 10. Go to github to merge the `bump_$VERSION` branch into release
 
-Don't delete the leftover branch just yet, as we will need it for the next step.
-
-### 11. Go to github to merge the `bump_$VERSION` branch into docs
-
-Merging the pull request to the docs branch will automatically
-update the documentation on the "latest" revision of the docs. You
-should see the updated docs 5-10 minutes after the merge. The docs
-will appear on http://docs.docker.io/. For more information about
-documentation releases, see `docs/README.md`.
-
 Don't forget to push that pretty blue button to delete the leftover
 branch afterwards!
 
+### 11. Update the docs branch
+
+```bash
+git checkout docs
+git fetch
+git reset --hard origin/release
+git push -f origin docs
+```
+
+Updating the docs branch will automatically update the documentation on the
+"latest" revision of the docs. You should see the updated docs 5-10 minutes
+after the merge. The docs will appear on http://docs.docker.io/. For more
+information about documentation releases, see `docs/README.md`.
+
 ### 12. Create a new pull request to merge release back into master
 
 ```bash