Temporarily pin django-otp to an older version, later breaks django-two-factor-auth.

requirements.txt

@@ -15,6 +15,7 @@ django-filter==2.2.0
 django-fsm==2.6.1
 django-heroku==0.3.1
 django-hijack==2.1.10
+django-otp==0.7.5 # Temporarily pin to an older version, later breaks django-two-factor-auth.
 django-pagedown==2.0.3
 django-pwned-passwords==4.1.0
 django-redis==4.11.0