DOC: Correct return type for DataFrame.hist

[MarcoGorelli]

The current return type that's documented is too broad, I think. It looks to me like it's always a 2D ndarray of Axes

Indeed, make_subplots is called with squeeze=False

pandas/pandas/plotting/_matplotlib/hist.py

Lines 549 to 552 in d18f9a2

	fig, axes = create_subplots(
	naxes=naxes,
	ax=ax,
	squeeze=False,

and in there there's:

pandas/pandas/plotting/_matplotlib/tools.py

Lines 319 to 321 in edf00e9

	else:
	# returned axis array will be always 2-d, even if nrows=ncols=1
	axes = axarr.reshape(nrows, ncols)

• closes #xxxx (Replace xxxx with the GitHub issue number)
• Tests added and passed if fixing a bug or adding a new feature
• All code checks passed.
• Added type annotations to new arguments/methods/functions.
• Added an entry in the latest doc/source/whatsnew/vX.X.X.rst file if fixing a bug or adding a new feature.

[mroeschke]

Thanks @MarcoGorelli