Revert "Add GPION to rigctld.c"

This reverts commit f926868dad.

tests/rigctld.c

@@ -356,10 +356,6 @@ int main(int argc, char *argv[])
             {
                 ptt_type = RIG_PTT_GPIO;
             }
-            else if (!strcmp(optarg, "GPION"))
-            {
-                ptt_type = RIG_PTT_GPION;
-            }
             else if (!strcmp(optarg, "NONE"))
             {
                 ptt_type = RIG_PTT_NONE;