tox: remove deprecated targets (#75439)

tox.ini

@@ -8,14 +8,12 @@ toxworkdir = {env:TMPDIR:/tmp}/tox-{env:USER}/authentic/
 envlist =
   update-locales
   py3
-  py3-buster
-  py3-bullseye
   py3-stable-backports
   check-migrations
   code-style
   pylint
 labels =
-  jenkins = update-locales,py3-bullseye,check-migrations,code-style,pylint
+  jenkins = update-locales,py3-stable-backports,check-migrations,code-style,pylint
 
 [testenv]
 setenv =
@@ -46,27 +44,11 @@ passenv=
   PYTESTOPTIONS
 deps = 
   pip > 9
-  buster: django<2.3
-  buster: django-model-utils<4
-  buster: django-select2>=5,<6
-  buster: dnspython==1.16.0
-# impossible to compile old version of pillow on recent debian :/ or to install
-# python3.6, the version of python on buster
-# buster: pillow==5.4.1
-  bullseye: django<2.3
-  bullseye: django-model-utils<4
-  bullseye: dnspython==2.0.0
-  bullseye: django-select2>=5,<6
-  bullseye: pillow==8.1.2
   stable-backports: django>=3.2.12,<3.3
   stable-backports: django-model-utils>=4.2,<4.3
   stable-backports: django-select2>=7.7,<7.8
-  buster: django-tables2==1.21.1
-  bullseye: django-tables2==2.1.1
   stable-backports: django-tables2==2.4.1
   psycopg2-binary
-  buster: psycopg2-binary<2.9
-  bullseye: psycopg2-binary<2.9
   coverage
   pytest-cov
   pytest-django
@@ -89,11 +71,7 @@ deps =
   ldaptools>=0.24
   numpy
   django-filter
-  buster: djangorestframework>=3.9.2,<3.10
-  bullseye: djangorestframework>=3.12,<3.13
   stable-backports: djangorestframework>=3.12,<3.13
-  buster: jwcrypto<0.9
-  bullseye: jwcrypto<0.9
   stable-backports: jwcrypto<0.9
 usedevelop = True
 allowlist_externals =