[TODO] service/server: note to remove override that will become useless

The method override `_handle_request_noblock`
is there to solve a bug in Python socketserver library
which has been solved in
- Python 3.6: python/cpython@8b1f52b5a9,
- Python 3.7: python/cpython@9080824513,

through PR python/cpython#9952.

These revisions will be included in Python releases 3.6.8 and 3.7.2,
and the override will then become useless.
We therefore can remove the `_handle_request_noblock` override
as soon as the Python 3 releases installed on operating systems
supported by Odoo are above
- 3.6.8 for Python 3.6
- 3.7.2 for Python 3.7

closes odoo/odoo#29706

odoo/service/server.py

@@ -160,6 +160,11 @@ class ThreadedWSGIServerReloadable(LoggingBaseWSGIServerMixIn, werkzeug.serving.
         t.start_time = time.time()
         t.start()
 
+    # TODO: Remove this method as soon as either of the revision
+    # - python/cpython@8b1f52b5a93403acd7d112cd1c1bc716b31a418a for Python 3.6,
+    # - python/cpython@908082451382b8b3ba09ebba638db660edbf5d8e for Python 3.7,
+    # is included in all Python 3 releases installed on all operating systems supported by Odoo.
+    # These revisions are included in Python from releases 3.6.8 and Python 3.7.2 respectively.
     def _handle_request_noblock(self):
         """
         In the python module `socketserver` `process_request` loop,