Merge branch 'autocomplete-find-user-improv' into 'master'

Improved Ruby code in autocomplete user search

## What does this MR do?

Improves the Ruby code for finding users in the assignee dropdown based on the Ruby review.

See merge request !7576

app/controllers/autocomplete_controller.rb

@@ -55,7 +55,7 @@ class AutocompleteController < ApplicationController
   def find_users
     @users =
       if @project
-        user_ids = @project.team.users.map(&:id)
+        user_ids = @project.team.users.pluck(:id)
 
         if params[:author_id].present?
           user_ids << params[:author_id]