Fix release workflow.

Publishing of release documentation failed with
'../latest' is outside repository [..]

.github/workflows/build.yaml

@@ -142,6 +142,6 @@ jobs:
           ./update_versions.sh
           git config user.name github-actions
           git config user.email github-actions@github.com
-          git add . ../latest
+          git add . latest
           git commit -m "Update documentation for release ${RELEASE}"
           git push