Fix some flash notices/alerts staying on unrelated pages (#11364)

app/controllers/admin/domain_blocks_controller.rb

@@ -17,7 +17,7 @@ module Admin
 
       if existing_domain_block.present? && !@domain_block.stricter_than?(existing_domain_block)
         @domain_block.save
-        flash[:alert] = I18n.t('admin.domain_blocks.existing_domain_block_html', name: existing_domain_block.domain, unblock_url: admin_domain_block_path(existing_domain_block)).html_safe # rubocop:disable Rails/OutputSafety
+        flash.now[:alert] = I18n.t('admin.domain_blocks.existing_domain_block_html', name: existing_domain_block.domain, unblock_url: admin_domain_block_path(existing_domain_block)).html_safe # rubocop:disable Rails/OutputSafety
         @domain_block.errors[:domain].clear
         render :new
       else

app/controllers/settings/two_factor_authentication/confirmations_controller.rb

@@ -14,7 +14,7 @@ module Settings
 
       def create
         if current_user.validate_and_consume_otp!(confirmation_params[:code])
-          flash[:notice] = I18n.t('two_factor_authentication.enabled_success')
+          flash.now[:notice] = I18n.t('two_factor_authentication.enabled_success')
 
           current_user.otp_required_for_login = true
           @recovery_codes = current_user.generate_otp_backup_codes!

app/controllers/settings/two_factor_authentication/recovery_codes_controller.rb

@@ -10,7 +10,7 @@ module Settings
       def create
         @recovery_codes = current_user.generate_otp_backup_codes!
         current_user.save!
-        flash[:notice] = I18n.t('two_factor_authentication.recovery_codes_regenerated')
+        flash.now[:notice] = I18n.t('two_factor_authentication.recovery_codes_regenerated')
         render :index
       end
     end