fix: set FLASK_APP_SETTINGS env for k8s-deployment

[cmltaWt0]

The FLASK_APP_SETTINGS is missing for k8s-deployment causing the usage of the default Production config only.

[MoisesGSalas]

Thanks, in theory this shouldn't affect anyone in k8s because the default when unset was codejailservice.config.ProductionConfig

[cmltaWt0]

@MoisesGSalas Thanks!
The defaults are okay for a default configuration. However, we ended up with a completely broken instance (students ran crazy code without any restrictions – so the default configuration wasn't great) due to the absence of tutor patching. We needed to set the correct LIMITS, but were unable to do so because of the misconfiguration and lack of patching.

[MoisesGSalas]

On the topic of LIMITS, you might want to read the findings that Tim have been documenting related to NPROC: openedx/codejail#239. Is particularly relevant in the k8s case.