PYTHON-3295 Improve description of nested timeout() calls

Author: ShaneHarvey

pymongo/__init__.py

@@ -142,8 +142,8 @@ def timeout(seconds: Optional[float]) -> ContextManager:
           else:
               print(f"failed with non-timeout error: {exc!r}")
 
-    When nesting :func:`~pymongo.timeout`, the newly computed deadline is capped to at most
-    the existing deadline. The deadline can only be shortened, not extended.
+    When nesting :func:`~pymongo.timeout`, the nested deadline is capped by
+    the outer deadline. The deadline can only be shortened, not extended.
     When exiting the block, the previous deadline is restored::
 
       with pymongo.timeout(5):