Add _threading_local.local.__delattr__ back to the stub

pyproject.toml

@@ -21,6 +21,7 @@ extra_standard_library = [
     "_heapq",
     "_markupbase",
     "_random",
+    "_threading_local",
     "_tkinter",
     "_tracemalloc",
     "_warnings",

stdlib/_threading_local.pyi

@@ -14,3 +14,4 @@ class _localimpl:
 class local:
     def __getattribute__(self, name: str) -> Any: ...
     def __setattr__(self, name: str, value: Any) -> None: ...
+    def __delattr__(self, name: str) -> None: ...

test_cases/stdlib/test_threading.py

@@ -0,0 +1,12 @@
+import _threading_local
+import threading
+
+loc = threading.local()
+loc.foo = 42
+del loc.foo
+loc.baz = ["spam", "eggs"]
+del loc.baz
+
+l2 = _threading_local.local()
+l2.asdfasdf = 56
+del l2.asdfasdf