Further fix the release notes for refs #13147.

Mention of custom user models has been removed since UserCreationForm
didn't support custom user models anyway. Refs #19353.
Fixed #23008 -- Fixed typo causing bad migration dependencies.

Thanks semenov for the report and Florian for investigation.
Fixed #22907 -- Array contains must have same type.
Fixed #23013 -- Fixed removing unique_together/index_together constraints in migrations.

Thanks melinath for the report.
Ignored STATIC_ROOT and MEDIA_ROOT in makemessages

Also alleviate issues with weird file names typically found in
MEDIA_ROOT directories (#23010).
Thanks Tim Graham for the review.
Fixed #22998 -- Updated the fast_delete logic for GFKs
PEP8 cleanup
Added forgotten files from commit 28efafa24c83
Added Chrome/IE support for a selenium test.
Fixed #23023 -- Added warning against local-memory cache.

Thanks django at kerz.id.au.
Fixed #23041: Bad base dependencies for proxy models
Fixed reference to pk in RedirectView.get_redirect_url doc.
Added 1.6.6 release notes for #22998 (also forwardported those for #13794).
Alphabetized django.utils sections.
Edited setup.py in reuseable apps tutorial to use a context manager for open().
Fixed #23028: Added unique_togther support to inspectdb.
Fixed #23043: alter_field drops defaults too
Fixed #23039: Don't try to serialize unmanaged models in tests
Fixed #22975: Don't call rename SQL if not needed
Fixed #23009: Shorten FK identifiers in add_field and make consistent