Remove Django 4.1 warning

[jedie]

e.g.: https://github.com/radiac/django-tagulous/runs/7107977655?check_suite_focus=true#step:5:20

../../../../../opt/hostedtoolcache/Python/3.6.15/x64/lib/python3.6/site-packages/django/apps/registry.py:91
/opt/hostedtoolcache/Python/3.6.15/x64/lib/python3.6/site-packages/django/apps/registry.py:91:
RemovedInDjango41Warning: 'tagulous' defines default_app_config = 'tagulous.apps.TagulousConfig'.
Django now detects this configuration automatically. You can remove default_app_config.
    app_config = AppConfig.create(entry)

[codecov-commenter]

Codecov Report

Merging #169 (25298f8) into develop (1617a62) will decrease coverage by 0.38%. The diff coverage is n/a.

@@             Coverage Diff             @@
##           develop     #169      +/-   ##
===========================================
- Coverage    99.56%   99.18%   -0.39%     
===========================================
  Files           28       28              
  Lines         1840     1839       -1     
===========================================
- Hits          1832     1824       -8     
- Misses           8       15       +7     

Impacted Files	Coverage Δ
tagulous/__init__.py	100.00% <ø> (ø)
tagulous/admin.py	97.39% <0.00%> (-2.61%)	:arrow_down:
tagulous/models/tagged.py	98.38% <0.00%> (-1.62%)	:arrow_down:
tagulous/forms.py	97.85% <0.00%> (-0.72%)	:arrow_down:

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[jedie]

@radiac ping