add ignore for new mypy error 'type-var' (#47766)

* add mypy 'type-var' ignore

* return NDFrame instead of NDFrameT to fix type-var error

* add # type: ignore[override] back

Author: anilbey

pandas/core/resample.py

@@ -205,7 +205,7 @@ def __getattr__(self, attr: str):
 
     # error: Signature of "obj" incompatible with supertype "BaseGroupBy"
     @property
-    def obj(self) -> NDFrameT:  # type: ignore[override]
+    def obj(self) -> NDFrame:  # type: ignore[override]
         # error: Incompatible return value type (got "Optional[Any]",
         # expected "NDFrameT")
         return self.groupby.obj  # type: ignore[return-value]