Tools: remove command-line option enabling synthetic clock

it's always on, all the time

this has always been set for many years

Tools/autotest/pysim/util.py

@@ -416,7 +416,6 @@ def start_SITL(binary,
                gdb=False,
                gdb_no_tui=False,
                wipe=False,
-               synthetic_clock=True,
                home=None,
                model=None,
                speedup=1,
@@ -516,8 +515,6 @@ def start_SITL(binary,
     if not supplementary:
         if wipe:
             cmd.append('-w')
-        if synthetic_clock:
-            cmd.append('-S')
         if home is not None:
             cmd.extend(['--home', home])
         cmd.extend(['--model', model])

Tools/autotest/sim_vehicle.py

@@ -766,7 +766,6 @@ def start_vehicle(binary, opts, stuff, spawns=None):
         cmd.extend(strace_options)
 
     cmd.append(binary)
-    cmd.append("-S")
     if opts.wipe_eeprom:
         cmd.append("-w")
     cmd.extend(["--model", stuff["model"]])