fix: allow tinting 'tick' icon

[david-allison]

I found it hard to find, so added some greppable strings

It also was not tintable, which made it invisible in any Material3 dialogs using it

Testing: unchanged

Testing: now working

Checklist

• You have a descriptive commit message with a short title (first line, max 50 chars).
• You have commented your code, particularly in hard-to-understand areas
• You have performed a self-review of your own code
• UI changes: include screenshots of all affected screens (in particular showing any new or changed strings)
• UI Changes: You have tested your change using the Google Accessibility Scanner