Removed database extra from django-constance

The `[database]` extra was removed in `django-constance` v3.0.0, in this
commit:
jazzband/django-constance@2cb2ccd#diff-60f61ab7a8d1910d86d9fda2261620314edcae5894d5aaa236b821c7256badd7.

requirements.txt

@@ -3,7 +3,7 @@ Django==4.1.7
 django-hosts==5.2
 django-ckeditor==6.7.0
 django-cleanup==8.0.0
-django-constance[database]==3.1.0
+django-constance==3.1.0
 django-decorator-include==3.0
 # (See this page for a list of all management commands: https://django-extensions.readthedocs.io/en/latest/command_extensions.html)
 django-extensions==3.2.3