chore(ci): update librarian workflow names (googleapis#13391)

Update librarian workflow names, so they are unified and easier to
identify.

Author: zhumin8

.github/workflows/librarian_generation_check.yaml

@@ -11,7 +11,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
-name: Librarian generate diff check on pull requests
+name: Librarian - Generate diff check on pull requests
 on:
   pull_request:
 

.github/workflows/showcase-version-check.yaml

@@ -12,7 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-name: Showcase Version Check
+name: Librarian - Showcase Version Check
 
 on:
   schedule:

.github/workflows/update_librarian_googleapis.yaml

@@ -12,7 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-name: Update librarian googleapis commitish
+name: Librarian - Update googleapis commitish and generate all
 on:
   schedule:
   - cron: '0 3 * * *' # Run once a day at 3:00 AM UTC