Update pint_array.py

Delete the last vestiges of some old code from a different PR.

Also use Pandas public APIs for `infer_dtype` (used in `_from_factorized`).

Signed-off-by: Michael Tiemann <[email protected]>

pint_pandas/pint_array.py

@@ -320,11 +320,6 @@ def __setitem__(self, key, value):
  # doing nothing here seems to be ok
  return
 
- try:
- next(i for i in self._data if pd.notna(i))
- except StopIteration:
- pass
-
  if isinstance(value, _Quantity):
  value = value.to(self.units).magnitude
  elif is_list_like(value) and len(value) > 0:
@@ -557,7 +552,7 @@ def _from_sequence_of_strings(cls, scalars, dtype=None, copy=False):
 
  @classmethod
  def _from_factorized(cls, values, original):
- from pandas._libs.lib import infer_dtype
+ from pandas.api.types import infer_dtype
 
  if infer_dtype(values) != "object":
  values = pd.array(values, copy=False)