coredevice: remove obsolete watchdog code (#1458)

artiq/coredevice/comm_kernel.py

@@ -36,7 +36,6 @@ class Reply(Enum):
 
     RPCRequest = 10
 
-    WatchdogExpired = 14
     ClockFailure = 15
 
 
@@ -627,8 +626,6 @@ class CommKernel:
                 self._serve_rpc(embedding_map)
             elif self._read_type == Reply.KernelException:
                 self._serve_exception(embedding_map, symbolizer, demangler)
-            elif self._read_type == Reply.WatchdogExpired:
-                raise exceptions.WatchdogExpired
             elif self._read_type == Reply.ClockFailure:
                 raise exceptions.ClockFailure
             else:

artiq/coredevice/exceptions.py

@@ -104,10 +104,6 @@ class DMAError(Exception):
     artiq_builtin = True
 
 
-class WatchdogExpired(Exception):
-    """Raised when a watchdog expires."""
-
-
 class ClockFailure(Exception):
     """Raised when RTIO PLL has lost lock."""