Ignore typeshed test files (#17249)

During the last typehed update, we included the `@tests` folder which is
unnecessary for mypy.
Update the `sync-typeshed.py` script to exclude it in the future.

Refs:
- #17246
- python/typeshed#11762

---------

Co-authored-by: Shantanu <[email protected]>
Co-authored-by: AlexWaygood <[email protected]>

Author: 3 people

misc/sync-typeshed.py

@@ -51,7 +51,9 @@ def update_typeshed(typeshed_dir: str, commit: str | None) -> str:
     # Remove existing stubs.
     shutil.rmtree(stdlib_dir)
     # Copy new stdlib stubs.
-    shutil.copytree(os.path.join(typeshed_dir, "stdlib"), stdlib_dir)
+    shutil.copytree(
+        os.path.join(typeshed_dir, "stdlib"), stdlib_dir, ignore=shutil.ignore_patterns("@tests")
+    )
     shutil.copy(os.path.join(typeshed_dir, "LICENSE"), os.path.join("mypy", "typeshed"))
     return commit