Add remove from followers api (#16864)

* Add followed_by? to account_interactions

* Add RemoveFromFollowersService

* Fix AccountBatch to use RemoveFromFollowersService

* Add remove from followers API

spec/models/concerns/account_interactions_spec.rb

@@ -360,6 +360,23 @@ describe AccountInteractions do
     end
   end
 
+  describe '#followed_by?' do
+    subject { account.followed_by?(target_account) }
+
+    context 'followed by target_account' do
+      it 'returns true' do
+        account.passive_relationships.create(account: target_account)
+        is_expected.to be true
+      end
+    end
+
+    context 'not followed by target_account' do
+      it 'returns false' do
+        is_expected.to be false
+      end
+    end
+  end
+
   describe '#blocking?' do
     subject { account.blocking?(target_account) }