Hide Adding Option Link for Locked Option Groups

You can edit option values from a few different places:

1. civicrm/admin/options?gid=<option_group_id>
2. civicrm/admin/options/<option_group_name>
3. civicrm/admin/custom/group/field/option?action=browse&gid=<custom_group_id>&fid=<custom_field_id>

When "is_locked" = 1 only the first method hides the button to add new option values.

The button to add an option value should be hidden for the two places where it is highlighted in the above screenshots

From Option Group Edit Page Using Group ID

This works as expected and the button to add a new option is hidden

From Custom Field Edit page

From Option Group Edit Page Using Group Name