Drop namespace from config option

[kannon92]

What would you like to be added:

We should drop namespace from the config option and take the namespace that the serviceaccount for JobSet lives under.

Why is this needed:
#719 (comment)

It is unclear the behavior that would happen if someone installs jobset into namespace x and the configuration is using namespace y. In the thread we discussed potentially dropping the namespace field from the config and using the namespace in serviceAccount.

[kannon92]

cc @andreyvelich @ahg-g @danielvegamyhre