Move already in use Rails rules to basic cops

We were already applying the FindEach rule since commit cae210c1, while
the EnumUniqueness rule is essential when we use `enum`, and the
EnvironmentComparison rule is very useful since it forces us to use a
format the UnknownEnv rule will recognize.

.rubocop.yml

@@ -15,18 +15,9 @@ Performance/EndWith:
 Performance/StartWith:
   Enabled: true
 
-Rails/EnumUniqueness:
-  Enabled: true
-
-Rails/EnvironmentComparison:
-  Enabled: true
-
 Rails/Exit:
   Enabled: true
 
-Rails/FindEach:
-  Enabled: true
-
 Rails/HasAndBelongsToMany:
   Enabled: true
 

.rubocop_basic.yml

@@ -191,9 +191,18 @@ Rails/DynamicFindBy:
   Enabled: true
   Severity: refactor
 
+Rails/EnumUniqueness:
+  Enabled: true
+
+Rails/EnvironmentComparison:
+  Enabled: true
+
 Rails/FindBy:
   Enabled: true
 
+Rails/FindEach:
+  Enabled: true
+
 Rails/HttpPositionalArguments:
   Enabled: true