Improve docstring for timeout param in unit_of_work decorator. (#828)

Co-authored-by: Robsdedude <rouven.bauer@neo4j.com>

Author: stefano-ottolenghi

neo4j/work/simple.py

@@ -477,6 +477,8 @@ def count_people_tx(tx):
         Transactions that execute longer than the configured timeout will be terminated by the database.
         This functionality allows to limit query/transaction execution time.
         Specified timeout overrides the default timeout configured in the database using ``dbms.transaction.timeout`` setting.
+        Values higher than ``dbms.transaction.timeout`` will be ignored and
+        will fall back to default (unless using Neo4j < 4.2).
         Value should not represent a duration of zero or negative duration.
     :type timeout: float or :const:`None`
     """