Remove/fix margins for logistration page with enterprise context.

lms/static/sass/views/_login-register.scss

@@ -10,16 +10,18 @@
     height: 100%;
     padding-left: $baseline;
     padding-right: $baseline;
+    margin-left: auto;
   }
 
   .login-register.border-left {
     border-left: 1px solid #d9d9d9;
     padding-left: ($baseline*1.5);
     padding-right: $baseline;
+    margin-left: 0;
   }
 }
 
-@media (max-width: 767px) {
+@include media-breakpoint-down(md) {
   .enterprise-content {
     margin: auto auto;
     display: block;