UX: Change wording for 'regular' categories to 'normal' (#17134)

At some point in the past we decided to rename the 'regular' notification state of topics/categories to 'normal'. However, some UI copy was missed when the initial renaming was done so this commit changes the spots that were missed to the new name.

db/post_migrate/20220617151846_rename_default_categories_regular_setting.rb

@@ -0,0 +1,19 @@
+# frozen_string_literal: true
+
+class RenameDefaultCategoriesRegularSetting < ActiveRecord::Migration[7.0]
+  def up
+    execute <<~SQL
+      UPDATE site_settings
+      SET name = 'default_categories_normal'
+      WHERE name = 'default_categories_regular'
+    SQL
+  end
+
+  def down
+    execute <<~SQL
+      UPDATE site_settings
+      SET name = 'default_categories_regular'
+      WHERE name = 'default_categories_normal'
+    SQL
+  end
+end