chore: Remove django.admin

[markstory]

We haven't used django-admin in a long time and it was recently disabled in self-hosted (#52329)

Given that we don't use it in saas, and it is not part of any common development workflows I think it is time to not include django-admin in our installed app list.

[asottile-sentry]

[dashed]

@markstory Don't forget to remove this

sentry/src/sentry/db/router.py

Line 49 in 2349aaf

"django_admin_log",

and to DROP TABLE django_admin_log;

[codecov]

Codecov Report

Merging #52679 (f099864) into master (2349aaf) will decrease coverage by 0.01%.
The diff coverage is n/a.

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #52679      +/-   ##
==========================================
- Coverage   79.37%   79.36%   -0.01%     
==========================================
  Files        4920     4920              
  Lines      206402   206397       -5     
  Branches    35286    35285       -1     
==========================================
- Hits       163823   163817       -6     
- Misses      37555    37559       +4     
+ Partials     5024     5021       -3     

Impacted Files	Coverage Δ
src/sentry/conf/server.py	91.71% <ø> (-0.02%)	⬇️
src/sentry/conf/urls.py	100.00% <ø> (+21.42%)	⬆️

... and 7 files with indirect coverage changes

[chadwhitacre]

@markstory These are okay?

$ ag 'django.*admin'
CHANGES
3434:  conflict with the Django admin.

src/bitfield/admin.py
1:from django.contrib.admin import FieldListFilter
2:from django.contrib.admin.options import IncorrectLookupParameters

src/social_auth/admin.py
1:from django.contrib import admin

src/sentry/silo/README.md
41:> Could not find silo assignment for django_admin_log

src/sentry/db/router.py
49:        "django_admin_log",

[markstory]

@chadwhitacre I think so. The bitfield and social_auth code won't run unless it is imported, and even if that code is imported, django.contrib.admin is still installed (as it comes with django) we're just no longer including the views/urls in our django application.

@dashed I'll see if I can write a migration to remove that table. I don't think we'll be able to remove the routing line until the next squash migration as the table will be in our migration history until then.