This:
* Fixes some broken references
* Cleans up some use of Python 2 aliases:
  * Switches references to `np.string_` to describe `np.bytes_` instead
  * Switches references to `np.unicode_` to describe `np.str_` instead

* DOC: Fixes for 18 broken links

This, with PR #16465, should fix nearly all the remaining broken links
on the site. 4 or 5 others should be easy to fix and just
need attention from someone more knowledgeable -- will
open an issue. For release notes with dead links,
I could usually find links on archive.org for roughly contemporary
versions.

* DOC: Update to "Fixes for 18 broken links #16472"

* Obsolete links, previously commented out, now deleted:
https://github.com/numpy/numpy/pull/16472#discussion_r433928958

* Semantic markup for reference to Python class:
https://github.com/numpy/numpy/pull/16472#discussion_r433553928

* Missing :ref: in internal link:
https://github.com/numpy/numpy/pull/16472#discussion_r433554484

Not included: Resolution on using external/internal doc link in .py:
https://github.com/numpy/numpy/pull/16472#discussion_r433554824

* DOC: Add internal link for 'Fixes for 18 broken links' PR #16472

Making reference [1] an internal link in function_base.py => numpy.vectorize.html

* DOC: Redirect 2 link fixes in PR #16472

* governance.rst link reverted
* ununcs.rst `overridden` link goes where it was meant to


per https://github.com/numpy/numpy/pull/16472#pullrequestreview-424666070

Fix missing np prefix.

Fix missing definitions.

Use print function instead of the statement.

Add seed to make output repeatable.

DOC: Resolve bad references in Sphinx warnings