Revert "bpo-27657: Fix urlparse() with numeric paths (GH-661)" (#18526)

Revert "bpo-27657: Fix urlparse() with numeric paths (GH-661)" (#18526)

This reverts commit 82b5f6b16e051f8a2ac6e87ba86b082fa1c4a77f.

The change broke the backwards compatibility of parsing behavior in a
patch release of Python (3.7.6). A decision was taken to revert this
patch in 3.7.7.

In https://bugs.python.org/issue27657 it was decided that the previous
behavior like

>>> urlparse('localhost:8080')
ParseResult(scheme='', netloc='', path='localhost:8080', params='', query='', fragment='')

>>> urlparse('undefined:8080')
ParseResult(scheme='', netloc='', path='undefined:8080', params='', query='', fragment='')

needs to be preserved in patch releases as number of users rely upon it.

Explicitly mention the releases involved with the revert in NEWS.
Adopt the wording suggested by @ned-deily.