feat(core): enable topic update narration by default and promote to general (#25586)

Co-authored-by: JAYADITYA <96861162+JayadityaGit@users.noreply.github.com>
Co-authored-by: Jack Wotherspoon <jackwoth@google.com>

.gemini/settings.json

@@ -2,8 +2,7 @@
   "experimental": {
     "extensionReloading": true,
     "modelSteering": true,
-    "memoryManager": true,
-    "topicUpdateNarration": true
+    "memoryManager": true
   },
   "general": {
     "devtools": true