ci: disable test that fails on all Juju versions

[dimaqq]

Description

Disable the test that fails on all Juju versions.

I suspect that it's due base incompatibility:

• ubuntu goes first and is available on 24.04
• ntp goes next, but it tops out at 22.04 on the default channel

Ref: #1267

[dimaqq]

This PR only addresses the one test that fails across all juju versions.
It does not address the other 8 tests that fail on Juju 3.3 specifically.

[benhoyt]

Change looks okay to me, thanks.

Integration tests are now failing with a couple of "juju.errors.JujuError: base: ubuntu@24.04/stable" errors. Boy, that's not a very helpful error message, is it? Are we missing part of the error?

[dimaqq]

/build

[dimaqq]

/merge

[dimaqq]

@benhoyt nope, that's that's the whole error that Juju 3.3 sends in the jRPC response. It basically means something like "field base, bad value ubuntu@24.04/stable".