Use default env vars in sky launch

[sentry-io[bot]]

🔍 Existing Issues For Review

Your pull request is modifying functions with the following pre-existing issues:

📄 File: runhouse/resources/hardware/on_demand_cluster.py

Function	Unhandled Issue
up	TypeError: argument of type 'NoneType' is not iterable app in li... Event Count: 1
up	ValueError: Invalid instance type 'L4' for cloud GCP. main in... Event Count: 1
up	TypeError: argument of type 'NoneType' is not iterable generic ASGI r... Event Count: 1
up	ValueError: Failed to restart server recsys-cluster main in <modu... Event Count: 1

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[carolineechen]

• #926 👈
• main

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[carolineechen]

setting env in sky task doesn't actually set the env vars for the cluster, just for running the sky task