Enable Lint/LiteralInCondition rubocop cop

Checks of literals used in conditions.

See #17478

.rubocop.yml

@@ -878,7 +878,7 @@ Lint/InvalidCharacterLiteral:
 
 # Checks of literals used in conditions.
 Lint/LiteralInCondition:
-  Enabled: false
+  Enabled: true
 
 # Checks for literals used in interpolation.
 Lint/LiteralInInterpolation:

app/models/ability.rb

@@ -25,18 +25,17 @@ class Ability
 
     # List of possible abilities for anonymous user
     def anonymous_abilities(user, subject)
-      case true
-      when subject.is_a?(PersonalSnippet)
+      if subject.is_a?(PersonalSnippet)
         anonymous_personal_snippet_abilities(subject)
-      when subject.is_a?(ProjectSnippet)
+      elsif subject.is_a?(ProjectSnippet)
         anonymous_project_snippet_abilities(subject)
-      when subject.is_a?(CommitStatus)
+      elsif subject.is_a?(CommitStatus)
         anonymous_commit_status_abilities(subject)
-      when subject.is_a?(Project) || subject.respond_to?(:project)
+      elsif subject.is_a?(Project) || subject.respond_to?(:project)
         anonymous_project_abilities(subject)
-      when subject.is_a?(Group) || subject.respond_to?(:group)
+      elsif subject.is_a?(Group) || subject.respond_to?(:group)
         anonymous_group_abilities(subject)
-      when subject.is_a?(User)
+      elsif subject.is_a?(User)
         anonymous_user_abilities
       else
         []

app/models/project_services/irker_service.rb

@@ -70,7 +70,7 @@ class IrkerService < Service
   private
 
   def get_channels
-    return true unless :activated?
+    return true unless activated?
     return true if recipients.nil? || recipients.empty?
 
     map_recipients

lib/gitlab/github_import/pull_request_formatter.rb

@@ -79,10 +79,9 @@ module Gitlab
       end
 
       def state
-        @state ||= case true
-                   when raw_data.state == 'closed' && raw_data.merged_at.present?
+        @state ||= if raw_data.state == 'closed' && raw_data.merged_at.present?
                      'merged'
-                   when raw_data.state == 'closed'
+                   elsif raw_data.state == 'closed'
                      'closed'
                    else
                      'opened'