waybar: drop unused children-class from tray drawer

No CSS rule targets .tray-drawer-child — speculative key with no
consumer. YAGNI cleanup.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

docs/superpowers/specs/2026-04-30-waybar-tray-drawer-design.md

@@ -41,7 +41,6 @@ Replace `"tray"` in `modules-right` with `"group/tray-drawer"`. Add the group de
   "orientation": "horizontal",
   "drawer": {
     "transition-duration": 200,
-    "children-class": "tray-drawer-child",
     "transition-left-to-right": true,
     "click-to-reveal": true
   },

waybar/config.jsonc

@@ -77,7 +77,6 @@
     "orientation": "horizontal",
     "drawer": {
       "transition-duration": 200,
-      "children-class": "tray-drawer-child",
       "transition-left-to-right": true,
       "click-to-reveal": true
     },