Fix small fonts in theme code

[NotherNgineer]

The "themes" code (in PR #2166) was incorrectly displaying "bg_lightest_small" text in large font, versus small.

This issue is visible in stack dumps (when DFU button is pressed following a fault), as in this photo:

I also removed some unnecessary "ui::" just for consistency.

[Brumi-2021]

To me it looks like correct ,
amending the previous too big font size definition in the light_white_background_font_size.

Accidentally we found it in the gcc 13.2.1 debugging investigation .
It should be fine.