DOC: Save File Image not found when generating Docs in parallel

[bhavaniravi]

Problem description

As a part of #27804 I tried adding num-jobs=4 while generating docs. But the doc generation part fails since doc/source/whatsnew/v0.7.3.rst file refers to an image in ../savefig/scatter_matrix_kde.png which is not generated from doc/source/user_guide/visualization.rst

Proposed solutions

Few solutions from the top of my mind

1. We can move these referenced files and have a static copy in _static(there are only 4 files we need to copy)
2. Remove these references from the v0.7.3 since it is outdated

Discussing this with @datapythonista open to the community's thought on this.

[datapythonista]

Since 0.7.3 is more than 7 years old, I think removing the 3 plots from the release notes is all right: https://pandas.pydata.org/pandas-docs/stable/whatsnew/v0.7.3.html

CC @TomAugspurger

[TomAugspurger]

Sounds good.