Use Caracal's Magnum

[cityofships]

• Switch to Caracal release;
• Remove magnum-cluster-api driver.

To be merged after #1430.

[cityofships]

Perhaps should be merged without waiting for CI - Magnum's not tested.

[sd109]

FWIW unpinning the driver version here feels wrong to me. Since we're not 100% in control of upstream driver releases, we could in theory be broken if other upstream Magnum core reviewers start becoming more active in the driver lifecycle and publishing releases themselves. Maybe we could pin to minor version so that we still get automatic patch releases when rebuilding containers?

[cityofships]

FWIW unpinning the driver version here feels wrong to me. Since we're not 100% in control of upstream driver releases, we could in theory be broken if other upstream Magnum core reviewers start becoming more active in the driver lifecycle and publishing releases themselves. Maybe we could pin to minor version so that we still get automatic patch releases when rebuilding containers?

The goal of this PR was to remove Antelope's pin on Magnum itself and it scope crept a little bit. Whether to unpin the driver should be a separate discussion, so I'm just bumping its version here.