chore: remove Phase 2b smoke test artifacts (#27)

Removes two artifacts left on main after the Phase 2b smoke test for
the release-doc-sync action:
- .release-doc-sync gitlink (was a 160000-mode submodule pointer
  that the action created as a side effect; bug fixed in
  Developer-Tools-Directory v1.8.1)
- .smoke-test-marker (was used to force release.yml to fire past
  the paths-ignore filter)

Both are no longer needed.

Refs TMHSDigital/Developer-Tools-Directory#5.

Signed-off-by: 154358121+TMHSDigital@users.noreply.github.com
Made-with: Cursor

Signed-off-by: 154358121+TMHSDigital@users.noreply.github.com

Author: TMHSDigital