Fix bugfix-release.sh behavior when there is nothing to release

```
./tekton/bugfix-release.sh: line 17: return: can only `return' from a function or sourced script
```

It should be `exit` instead :)

Signed-off-by: Vincent Demeester <vdemeest@redhat.com>

tekton/bugfix-release.sh

@@ -14,7 +14,7 @@ TEKTON_RELEASE_NAME=$(gh release view v0.47.7 --json name | jq .name | sed -e 's
 
 if [[ "${TEKTON_RELEASE_GIT_SHA}" == "${TEKTON_OLD_VERSION_COMMIT_SHA}" ]]; then
     echo "> No new commit in ${RELEASE_BRANCH} (${TEKTON_RELEASE_GIT_SHA}==${TEKTON_OLD_VERSION_COMMIT_SHA})"
-    return 0
+    exit 0
 fi
 
 TEKTON_VERSION=$(echo ${TEKTON_OLD_VERSION} | awk -F. -v OFS=. '{$NF += 1 ; print}')