chore(clearbutton): metadata mods doc updated

Author: castastrophe

components/clearbutton/metadata/mods.md

@@ -1,11 +1,13 @@
 | Modifiable Custom Properties                    |
 | ----------------------------------------------- |
 | `--mod-clear-button-background-color`           |
+| `--mod-clear-button-background-color-disabled`  |
 | `--mod-clear-button-background-color-down`      |
 | `--mod-clear-button-background-color-hover`     |
 | `--mod-clear-button-background-color-key-focus` |
 | `--mod-clear-button-height`                     |
 | `--mod-clear-button-icon-color`                 |
+| `--mod-clear-button-icon-color-disabled`        |
 | `--mod-clear-button-icon-color-down`            |
 | `--mod-clear-button-icon-color-hover`           |
 | `--mod-clear-button-icon-color-key-focus`       |