fix: Make context manager __exit__/__aexit__ signatures compatible with typing protocols

Updates AsyncContextManager.__aexit__ and SyncContextManager.__exit__ to use
Optional types for exception parameters (exc_type, exc_val, traceback) to match
the standard Python typing protocols.

This aligns with the official type definitions in typeshed where
AbstractContextManager and AbstractAsyncContextManager define these parameters
as Optional since they are None when no exception occurs.

Ref: https://github.com/python/typeshed/blob/9317dc62bd4fb46b8b48ce5353286cab80308d47/stdlib/contextlib.pyi#L52-L54

Fixes type checker compatibility issues when using BrowserContext with
type checkers that enforce strict protocol compliance.

Author: mxschmitt

playwright/_impl/_async_base.py

@@ -96,9 +96,9 @@ async def __aenter__(self: Self) -> Self:
 
     async def __aexit__(
         self,
-        exc_type: Type[BaseException],
-        exc_val: BaseException,
-        traceback: TracebackType,
+        exc_type: Optional[Type[BaseException]],
+        exc_val: Optional[BaseException],
+        traceback: Optional[TracebackType],
     ) -> None:
         await self.close()
 

playwright/_impl/_sync_base.py

@@ -142,9 +142,9 @@ def __enter__(self: Self) -> Self:
 
     def __exit__(
         self,
-        exc_type: Type[BaseException],
-        exc_val: BaseException,
-        _traceback: TracebackType,
+        exc_type: Optional[Type[BaseException]],
+        exc_val: Optional[BaseException],
+        _traceback: Optional[TracebackType],
     ) -> None:
         self.close()