refactor: replace bare except with BaseException in AsyncQueue (#6765)

## Description
Replaced a bare `except:` with `except BaseException:` in
`libs/langgraph/langgraph/_internal/_queue.py`.

## Motivation
Using a bare `except:` violates PEP 8 (E722). While functionally
equivalent to `except BaseException:`, making it explicit improves code
readability and satisfies static analysis tools.

This ensures that `asyncio.CancelledError` (which inherits from
`BaseException`) is still caught and handled correctly by the
cancellation logic in the `wait()` method, but without the ambiguity of
a bare except.

libs/langgraph/langgraph/_internal/_queue.py

@@ -25,7 +25,7 @@ class AsyncQueue(asyncio.Queue):
             self._getters.append(getter)
             try:
                 await getter
-            except:
+            except BaseException:
                 getter.cancel()  # Just in case getter is not done yet.
                 try:
                     # Clean self._getters from canceled getters.