upgraded some django dependencies

requirements.txt

@@ -17,9 +17,9 @@ django-excel==0.0.10
 django-formtools==2.4.1
 django-npm==1.0.0
 django-otp==1.2.4
-django-phonenumber-field==7.2.0
+django-phonenumber-field==6.4.0
 django-stronghold==0.4.0
-django-two-factor-auth==1.15.5
+django-two-factor-auth==1.15.1
 enum34==1.1.10
 funcsigs==1.0.2
 gunicorn==21.2.0