docs: Fix shell code
Correct the shell code in the packaging tools README to keep the CI
happy.
@@ -34,7 +34,7 @@ $ ./update-repository-version.sh -h
To update project version for Kata Containers, use the following:
```bash
-$ make bump-kata-version NEW_VERSION=<new-version>
+$ make bump-kata-version NEW_VERSION="${new_version}"
```
The makefile target `bump-kata-version` creates a GitHub pull request in the
