[MINOR][PS] Fallback code clean up

### What changes were proposed in this pull request?
Fallback code clean up

### Why are the changes needed?
```
   DataFrame.to_feather
   DataFrame.to_stata
```

the two methods were already added as normal methods, no need to be in the fallback list

### Does this PR introduce _any_ user-facing change?
no

### How was this patch tested?
ci

### Was this patch authored or co-authored using generative AI tooling?
no

Closes #46784 from zhengruifeng/ps_fallback_cleanup.

Authored-by: Ruifeng Zheng <ruifengz@apache.org>
Signed-off-by: Ruifeng Zheng <ruifengz@apache.org>

python/pyspark/pandas/frame.py

@@ -13626,14 +13626,6 @@ def _set_axis_fallback(self, *args: Any, **kwargs: Any) -> "DataFrame":
         _f = self._build_fallback_method("set_axis")
         return _f(*args, **kwargs)
 
-    def _to_feather_fallback(self, *args: Any, **kwargs: Any) -> None:
-        _f = self._build_fallback_driver_method("to_feather")
-        return _f(*args, **kwargs)
-
-    def _to_stata_fallback(self, *args: Any, **kwargs: Any) -> None:
-        _f = self._build_fallback_driver_method("to_stata")
-        return _f(*args, **kwargs)
-
     def __getattr__(self, key: str) -> Any:
         if key.startswith("__"):
             raise AttributeError(key)