[2.7] bpo-36502: Update link to UAX GH-44, the Unicode doc on the UCD (GH-15301) by benjaminp · Pull Request #15808

[2.7] bpo-36502: Update link to UAX GH-44, the Unicode doc on the UCD (GH-15301) by benjaminp · Pull Request #15808 · python/cpython

GH-15301)

The link we have points to the version from Unicode 6.0.0, dated 2010.
There have been numerous updates to it since then:
  https://www.unicode.org/reports/tr44/GH-Modifications

Change the link to one that points to the current version. Also, use HTTPS..
(cherry picked from commit 64c6ac7)

Co-authored-by: Greg Price <gnprice@gmail.com>