err_admin_name_pattern_not_allowed String Clarification (#9731)

* err_admin_name_pattern_not_allowed clarification edit

* Apply suggestion from @zeripath

Context: username that provided as admin

Co-Authored-By: zeripath <art27@cantab.net>

Co-authored-by: zeripath <art27@cantab.net>
Co-authored-by: Antoine GIRARD <sapk@users.noreply.github.com>

options/locale/locale_en-US.ini

@@ -111,7 +111,7 @@ no_admin_and_disable_registration = You cannot disable user self-registration wi
 err_empty_admin_password = The administrator password cannot be empty.
 err_empty_admin_email = The administrator email cannot be empty.
 err_admin_name_is_reserved = Administrator Username is invalid, username is reserved
-err_admin_name_pattern_not_allowed = Administrator Username is invalid, username is pattern is not allowed
+err_admin_name_pattern_not_allowed = Administrator username is invalid, the username matches a reserved pattern
 err_admin_name_is_invalid = Administrator Username is invalid
 
 general_title = General Settings