Fix flaky test (#25965)

## Summary & Motivation

Following some breadcrumbs from the error message that would sometimes
get spit out, it seems like this should be set to True in test
scenarios.

## How I Tested These Changes

Hard to prove a negative, but I was able to repro the issue locally
within 5 runs of the suite, and after this change 10 local runs
succeeded

## Changelog

NOCHANGELOG

python_modules/dagster/dagster_tests/definitions_tests/declarative_automation_tests/daemon_tests/test_e2e.py

@@ -123,7 +123,7 @@ def get_grpc_workspace_request_context(filename: str, instance_ref: Optional[Ins
             instance_ref=instance.get_ref(),
             loadable_target_origin=get_loadable_target_origin(filename),
             max_workers=4,
-            wait_on_exit=False,
+            wait_on_exit=True,
         ) as server_process:
             target = GrpcServerTarget(
                 host="localhost",