chore(mods): drop superseded architectury/balm/defaultoptions + chat_heads keys

The distribution replaced architectury 13.0.8 -> 13.0.11, balm 21.0.58 ->
21.0.63 and defaultoptions 21.1.6 -> 21.1.7 (both versions of each were
briefly on disk, so both got classified and both were synced into /mods),
and dropped chat_heads. Removing the stale keys — sync-server-mods refuses
to run while a selected jar is missing from the distribution.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

mods-sides.json

@@ -55,18 +55,15 @@
   "amendments-neoforge-1.21-2.1.5.jar": "both",
   "appleskin-neoforge-mc1.21-3.0.9.jar": "client",
   "architectury-13.0.11-neoforge.jar": "both",
-  "architectury-13.0.8-neoforge.jar": "both",
   "ars_creo-1.21.1-5.4.0.jar": "both",
   "ars_nouveau-1.21.1-5.12.1.jar": "both",
   "ars_technica-1.21.1-2.7.6.jar": "both",
   "baguettelib-1.21.1-NeoForge-2.0.3.jar": "both",
-  "balm-neoforge-1.21.1-21.0.58.jar": "both",
   "balm-neoforge-1.21.1-21.0.63.jar": "both",
   "buildinggadgets2-1.3.9.jar": "both",
   "caelus-neoforge-7.0.1+1.21.1.jar": "both",
   "cardboardboxes-1.21.1-0.1.2.jar": "both",
   "charginggadgets-1.14.1.jar": "both",
-  "chat_heads-1.2.4-neoforge-1.21.11.jar": "client",
   "cloth-config-15.0.140-neoforge.jar": "both",
   "collective-1.21.1-8.39.jar": "both",
   "colorfulhearts-neoforge-1.21.1-10.5.9.jar": "client",
@@ -95,7 +92,6 @@
   "cupboard-1.21.1-3.9.jar": "both",
   "curios-neoforge-9.5.1+1.21.1.jar": "both",
   "cwb-neoforge-3.0.0+mc1.21.jar": "client",
-  "defaultoptions-neoforge-1.21.1-21.1.6.jar": "both",
   "defaultoptions-neoforge-1.21.1-21.1.7.jar": "both",
   "drippyloadingscreen_neoforge_3.1.2_MC_1.21.1.jar": "client",
   "easy-piglins-neoforge-1.21.1-1.1.0.jar": "both",