Update Gitlab CI example from v1 to v2

[fabio-looker]

I tried to just eyeball the update, but am not familiar enough with Gitlab CI.

@PieterjanCriel if you are still using LAMS, perhaps you could take a look? The update is quite simple I think (probably just deleting some no longer needed lines)

Similar update of Github Actions example from v1 to v2:
https://github.com/looker-open-source/look-at-me-sideways/pull/90/files#diff-5565610d10fa90d1b0be11c7f459812e0ddf7015e2d76c364d41d166b06dd43d