Bump Python requirement django-rq to 2.6.0

requirements.txt

@@ -5,7 +5,7 @@ django-admin-hstore-widget==1.2.0
 django-cors-headers==3.13.0
 django-enumfields==2.1.1
 django-pgtrigger==4.6.0
-django-rq==2.5.1
+django-rq==2.6.0
 djangorestframework==3.12.4
 drf-spectacular==0.18.2
 gitpython==3.1.27