DOC: hint that it might be a good idea to remove dist

RELEASE_GUIDELINES.md

@@ -28,7 +28,9 @@ guidelines of the CaosDB Project
 
 6. Delete the release branch.
 
-7. Publish the release by executing `./release.sh` with uploads the caosdb
+7. Remove possibly existing `./dist` directory with old release.
+
+8. Publish the release by executing `./release.sh` with uploads the caosdb
    module to the Python Package Index [pypi.org](https://pypi.org).
 
-8. Merge the master branch back into the dev branch.
+9. Merge the master branch back into the dev branch.