docs: add region tag around run/mcp-server/test_server.py (#13473)

* docs: add region tag around run/mcp-server/test_server.py

* chore: Update Dockerfile

* use common cloudrun_mcpserver_ prefix for all tags in this sample

---------

Co-authored-by: Katie McLaughlin <katie@glasnt.com>

Author: jackwotherspoon

run/mcp-server/Dockerfile

@@ -13,7 +13,6 @@
 # limitations under the License.
 
 # [START cloudrun_mcpserver_dockerfile_python]
-
 # Use the official Python image
 FROM python:3.13-slim
 

run/mcp-server/test_server.py

@@ -12,6 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+# [START cloudrun_mcpserver_test]
 import asyncio
 
 from fastmcp import Client
@@ -35,3 +36,4 @@ async def test_server():
 
 if __name__ == "__main__":
     asyncio.run(test_server())
+# [END cloudrun_mcpserver_test]