Update requirements.txt

Update django-mailer to be compatible with Django 4.2

Author: fallen

requirements.txt

@@ -1,7 +1,7 @@
 Django~=4.2.0
 django-colorfield==0.10.1
 django-tinymce==3.6.1
-django-mailer==1.2.6
+django-mailer==2.3
 django-maintenance-mode
 django-phonenumber-field[phonenumbers]==6.3.0
 requests~=2.20.0