remove TC driver destructor, cleanup

api/src/opentrons/drivers/thermocycler/driver.py

@@ -627,10 +627,3 @@ async def enter_programming_mode(self):
         await asyncio.sleep(0.05)
         trigger_connection.close()
         self.disconnect()
-
-    def __del__(self):
-        try:
-            if self._poller:
-                self._poller.close()  # type: ignore
-        except Exception:
-            log.exception('Exception while cleaning up Thermocycler')

api/src/opentrons/hardware_control/modules/thermocycler.py

@@ -349,4 +349,7 @@ async def prep_for_update(self):
         return new_port or self.port
 
     def cleanup(self) -> None:
-        self._driver.disconnect()
+        try:
+            self._driver.disconnect()
+        except Exception:
+            MODULE_LOG.exception('Exception while cleaning up Thermocycler')

api/src/opentrons/hardware_control/thread_manager.py

@@ -196,8 +196,8 @@ def __getattribute__(self, attr_name):
 
             # Update self._cached_modules to delete all removed modules' entries and add
             # newly attached modules. Removing references to stale instances
-            # is necessary to allow the garbage collector to delete those objects from
-            # memory and cleanly stop all the threads associated with them.
+            # is necessary in order to allow the garbage collector to delete
+            # those objects from memory and cleanly stop all associated threads.
             cached_mods = {
                     module: cached_mods.get(module, wrap(module)) for module in attr}
             object.__setattr__(self, '_cached_modules', cached_mods)