Fix `Rails/WhereExists` cop in app/models (#28863)

.rubocop_todo.yml

@@ -81,9 +81,6 @@ Rails/WhereExists:
     - 'app/lib/delivery_failure_tracker.rb'
     - 'app/lib/feed_manager.rb'
     - 'app/lib/suspicious_sign_in_detector.rb'
-    - 'app/models/poll.rb'
-    - 'app/models/session_activation.rb'
-    - 'app/models/status.rb'
     - 'app/policies/status_policy.rb'
     - 'app/serializers/rest/announcement_serializer.rb'
     - 'app/workers/move_worker.rb'

app/models/poll.rb

@@ -57,7 +57,7 @@ class Poll < ApplicationRecord
   end
 
   def voted?(account)
-    account.id == account_id || votes.where(account: account).exists?
+    account.id == account_id || votes.exists?(account: account)
   end
 
   def own_votes(account)

app/models/session_activation.rb

@@ -41,7 +41,7 @@ class SessionActivation < ApplicationRecord
 
   class << self
     def active?(id)
-      id && where(session_id: id).exists?
+      id && exists?(session_id: id)
     end
 
     def activate(**options)

app/models/status.rb

@@ -263,7 +263,7 @@ class Status < ApplicationRecord
   end
 
   def reported?
-    @reported ||= Report.where(target_account: account).unresolved.where('? = ANY(status_ids)', id).exists?
+    @reported ||= Report.where(target_account: account).unresolved.exists?(['? = ANY(status_ids)', id])
   end
 
   def emojis