Quarantine issue board label spec and remove reliable tag

qa/qa/specs/features/ee/browser_ui/2_plan/issue_boards/configure_issue_board_by_label_spec.rb

 # frozen_string_literal: true
 
 module QA
-  RSpec.describe 'Plan', :reliable do
+  RSpec.describe 'Plan', quarantine: { issue: 'https://gitlab.com/gitlab-org/gitlab/-/issues/344780', type: :flaky } do
     describe 'Configure issue board by label' do
       let(:label_board_list) do
         EE::Resource::Board::BoardList::Project::LabelBoardList.fabricate_via_api!