Revert snap base to electron-builder's default

Setting `base: core22` left the snap declaring a core22 base while still
plugging the core18-era gnome-3-28-1804 content snap for its GNOME platform.
Mesa's DRI drivers in that platform cannot resolve their dependencies against
core22, so every GL/EGL path fails including the swrast software fallback, the
GPU process exits, and the main process segfaults before a window appears.

The base override never moved the platform. electron-builder's snap template
pairs `base: core20` with a hardcoded `gnome-3-28-1804` plug, and its legacy
snap path rewrites only the `base` field, leaving the plugs block untouched.
The two halves have to match, so the fix is to stop overriding the base and
let the template stay self-consistent.

Dropping the key rather than pinning core20 explicitly means the snap keeps
following whatever electron-builder's template ships.

This restores the pre-3.68 behaviour, which reopens #2614 for very new GPUs
whose hardware needs a newer Mesa than the platform provides. That trade is
deliberate: #2614 affected some GPUs, this affects every user.

Fixes #3002

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01KboMatXCuTgjD6KfC1ik12

package.json

@@ -480,7 +480,6 @@
       ]
     },
     "snap": {
-      "base": "core22",
       "plugs": [
         "default",
         "removable-media"