chore(submodule): update simplesettings to v32.0.6 (drop file: deps)

Update apps-custom/simplesettings submodule pointer to commit 2df4b39:
- Bumps app version to 32.0.6
- Replaces file: deps with upstream npm packages (@mdi/js 7.4.47,
  @nextcloud/vue 8.35.3, vue-material-design-icons 5.3.1)

Ref: IONOS-Productivity/nc-simplesettings#171
Part of HDNEXT-1764 / HDNEXT-1719 (drop FA Pro icon mapping).

Author: printminion-co