Release note remove app

[wen-2018]

If this changeset needs to go into the FXC codebase, please add the WMO and FXC label.

One-line summary

This PR can only be merged after #17240 is deployed.

Significant changes and points to review

• removes release notes app entirely after DB clean up is complete.

Issue / Bugzilla link

#17225 (comment)

Testing

[janriokrause]

Looks good with some minor improvements:

1. After rebasing and the previous PR has landed, please do not forget to git rm bedrock/releasenotes/migrations/0003_delete_productrelease.py.

2. Remove releasenotes.ProductRelease \ from the dumpdata call in bin/export-db-to-sqlite.sh (line 196). It will break the export otherwise.

3. Fix the stale # For release notes. comment on "www.mozilla.org" in _csp_img_src in bedrock/settings/__init__.py, or drop the entry if nothing else needs it. Probably @stevejalim knows best.

4. Follow-up PR after this one merges: Remove django-memoize==2.3.1 from requirements/prod.in, then regenerate prod.txt + dev.txt.

[wen-2018]

Remove releasenotes.ProductRelease \ from the dumpdata call in bin/export-db-to-sqlite.sh (line 196). It will break the export otherwise.

This had been addressed in #17250

[janriokrause]

r+ Thank you!

[janriokrause]

Two quick follow-up notes:

1. django-memoize: already unused. The only memoize in the codebase is a local decorator in lib/l10n_utils/fluent.py, nothing imports from the django-memoize package, so dropping it from requirements/prod.in and regenerating prod.txt + dev.txt is safe to do whenever. (as mentioned above)

2. whatsnew-fx146-donate.html is dead code: WNP_145_PLUS_RE in bedrock/firefox/redirects.py unconditionally 301s /firefox/146.0/whatsnew/ to www.firefox.com, so the template is unreachable. Safe to remove along with:

   • firefox/whatsnew/whatsnew-fx146-donate.html entry in WhatsnewView.ftl_files_map (bedrock/firefox/views.py)
   • firefox_whatsnew_146_donate CSS bundle declaration
   • /media/img/firefox/whatsnew/whatsnew146/ image assets
   • whatsnew-donate-* Fluent strings in l10n/en/firefox/whatsnew/whatsnew.ftl if nothing else references them

Both are unrelated to the release-notes-app removal, so I'd keep them out of this PR and bundle them into two follow-ups. Feel free to pick it up or let me know if you don't have headspace.