fix: closes #11343's [attr-defined] type errors

On Windows 10.0.19045, the mypy hook is failing on pre-commit because of two [attr-defined] errors, which prevents me from staging stages. The problem was first reported in #11343. This PR solves the problem by adding `type ignore` comments to the erroring lines:

```
src\_pytest\compat.py:324: error: Module has no attribute "getuid"; maybe "getpid" or "getppid"?  [attr-defined]
testing\test_parseopt.py:294: error: Module has no attribute "getencoding"  [attr-defined]
```

src/_pytest/compat.py

@@ -321,7 +321,7 @@ def get_user_id() -> int | None:
         return None
     # getuid shouldn't fail, but cpython defines such a case.
     # Let's hope for the best.
-    uid = os.getuid()
+    uid = os.getuid()  # type: ignore[attr-defined]
     return uid if uid != -1 else None
 
 

testing/test_parseopt.py

@@ -291,7 +291,8 @@ class TestParser:
 
 def test_argcomplete(pytester: Pytester, monkeypatch: MonkeyPatch) -> None:
     try:
-        encoding = locale.getencoding()  # New in Python 3.11, ignores utf-8 mode
+        # New in Python 3.11, ignores utf-8 mode
+        encoding = locale.getencoding()  # type: ignore[attr-defined]
     except AttributeError:
         encoding = locale.getpreferredencoding(False)
     try: