Fixed doc requirements

Author: ellmetha

requirements-doc.freeze

@@ -14,7 +14,7 @@ Django==2.1
 django-debug-toolbar==1.9.1
 django-haystack==2.8.1
 django-js-asset==1.1.0
--e git+git@github.com:ellmetha/django-machina.git@611f3e2a8d1719c58cc3ba227b825e352dc321a9#egg=django_machina
+django-machina==0.7.1
 django-mptt==0.9.1
 django-widget-tweaks==1.4.2
 docutils==0.14