Remove seed file from the development env

This backport a change made in the CE upstream MR, see
https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/3593Signed-off-by: Rémy Coutable <remy@rymai.me>

db/fixtures/test/01_admin.rb

-require './spec/support/sidekiq'
-
-Gitlab::Seeder.quiet do
-  User.seed do |s|
-    s.id = 1
-    s.name = 'Administrator'
-    s.email = 'admin@example.com'
-    s.notification_email = 'admin@example.com'
-    s.username = 'root'
-    s.password = '5iveL!fe'
-    s.admin = true
-    s.projects_limit = 100
-    s.confirmed_at = DateTime.now
-  end
-end