test: stabilize stopped sandbox websocket test #1432

Job	Run time
Build (Web)	57s
TypeCheck (TypeScript)	48s
Lint & Format (Python - modal-infra)	22s
Lint & Format (TypeScript)	44s
TypeCheck (Python)	30s
Lint & Format (Python - sandbox-runtime)	17s
Test (Python - modal-infra)	32s
TypeCheck (Python - sandbox-runtime)	18s
Test (Python - sandbox-runtime)	21s
Test (control-plane integration)	1m 3s
Test (bots)	39s
Test (control-plane unit)	48s
Test (web)	45s
	8m 4s

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