fix(server): don't reuse ThreadPoolExecutor between grpc and runners (#…

…149)

src/isolate/server/server.py

@@ -467,7 +467,7 @@ def _add_log_to_queue(self, log: Log) -> None:
 
 def main() -> None:
     server = grpc.server(
-        RUNNER_THREAD_POOL,
+        futures.ThreadPoolExecutor(max_workers=MAX_THREADS),
         options=get_default_options(),
     )
     with BridgeManager() as bridge_manager: