chore(underlay): update mods

Author: jenndiaz

components/underlay/metadata/mods.md

@@ -1,13 +1,9 @@
 | Modifiable Custom Properties                         |
 | ---------------------------------------------------- |
 | `--mod-underlay-background-color`                    |
-| `--mod-underlay-background-color-rgb`                |
 | `--mod-underlay-background-entry-animation-delay`    |
 | `--mod-underlay-background-entry-animation-duration` |
 | `--mod-underlay-background-entry-animation-ease`     |
 | `--mod-underlay-background-exit-animation-delay`     |
 | `--mod-underlay-background-exit-animation-duration`  |
 | `--mod-underlay-background-exit-animation-ease`      |
-| `--mod-underlay-background-opacity-dark`             |
-| `--mod-underlay-background-opacity-darkest`          |
-| `--mod-underlay-background-opacity-light`            |