dorothy: suppress unnecessary git checkout feedback

/ref https://github.com/bevry/dorothy/actions/runs/8035566863/job/21948335670#step:2:12

commands/dorothy

@@ -852,7 +852,7 @@ function dorothy_() (
 			if test -n "$option_reference"; then
 				(
 					cd "$DOROTHY"
-					git checkout "$option_reference"
+					git checkout --quiet "$option_reference" # --quiet to suppress "detached HEAD" feedback
 				)
 			fi
 		}