Update session.py

Author: DenisStefanAndrei

src/mcp/shared/session.py

@@ -102,7 +102,7 @@ def __exit__(
         exc_type: type[BaseException] | None,
         exc_val: BaseException | None,
         exc_tb: TracebackType | None,
-    ) -> None:
+    ) -> bool:
         """Exit the context manager, performing cleanup and notifying completion."""
         try:
             if self._completed:  # pragma: no branch