Fix RuboCop offense Style/RedundantSelfAssignment (#39887).

git-svn-id: https://svn.redmine.org/redmine/trunk@22827 e93f8b46-1217-0410-a6f0-8f06a7374b81

.rubocop_todo.yml

@@ -1421,11 +1421,6 @@ Style/RedundantReturn:
 Style/RedundantSelf:
   Enabled: false
 
-# This cop supports unsafe autocorrection (--autocorrect-all).
-Style/RedundantSelfAssignment:
-  Exclude:
-    - 'lib/redmine/menu_manager.rb'
-
 # This cop supports safe autocorrection (--autocorrect).
 Style/RedundantSelfAssignmentBranch:
   Exclude:

lib/redmine/menu_manager.rb

@@ -381,7 +381,7 @@ module Redmine
 
       # Adds a child at given position
       def add_at(child, position)
-        @children = @children.insert(position, child)
+        @children.insert(position, child)
         child.parent = self
         child
       end