Upgrade has_scope

The previous version of has_scope doesn't support Rails 5. Support for
Rails 5 was introduced in version 7.0, but we may as well as go all the
way to 0.7.2 which is the last version that supports Rails < 5.2.

https://github.com/heartcombo/has_scope/blob/main/CHANGELOG.md#072

Gemfile.lock

@@ -160,9 +160,9 @@ GEM
       thor (~> 0.19.1)
     globalid (0.4.2)
       activesupport (>= 4.2.0)
-    has_scope (0.6.0)
-      actionpack (>= 3.2, < 5)
-      activesupport (>= 3.2, < 5)
+    has_scope (0.7.2)
+      actionpack (>= 4.1)
+      activesupport (>= 4.1)
     hashery (2.1.2)
     hashie (3.5.7)
     hitimes (1.3.1)