[scripts] SC2317: command appears to be unreachable (#10821)

script/test

@@ -706,12 +706,10 @@ main()
             cert)
                 shift
                 do_cert "$@"
-                shift $#
                 ;;
             cert_suite)
                 shift
                 do_cert_suite "$@"
-                shift $#
                 ;;
             get_thread_wireshark)
                 do_get_thread_wireshark

tests/nexus/build.sh

@@ -27,14 +27,6 @@
 #  POSSIBILITY OF SUCH DAMAGE.
 #
 
-display_usage()
-{
-    echo ""
-    echo "Nexus build script "
-    echo ""
-    echo ""
-}
-
 die()
 {
     echo " *** ERROR: " "$*"