chore: Remove toolchain section from language settings (#20168)

Closes #ISSUE

Release Notes:

- N/A

assets/settings/default.json

@@ -820,7 +820,6 @@
   "tasks": {
     "variables": {}
   },
-  "toolchain": { "name": "default", "path": "default" },
   // An object whose keys are language names, and whose values
   // are arrays of filenames or extensions of files that should
   // use those languages.