fix: Use TypeVar defaults correctly?

- I thought what I had was allowed
- but caused a runtime error in subclasses that *didn't* fill the missing `FromNumpyDT_contra`

> TypeError: Too few arguments for <class 'narwhals._compliant.dataframe.CompliantDataFrame'>; actual 3, expected at least 4

Author: dangotbanned

narwhals/_compliant/dataframe.py

@@ -49,7 +49,7 @@
 
 
 class CompliantDataFrame(
-    NumpyConvertible["_2DArray"],
+    NumpyConvertible["_2DArray", "_2DArray"],
     _StoresNative[NativeFrameT_co],
     Sized,
     Protocol[CompliantSeriesT, CompliantExprT_contra, NativeFrameT_co],