fix(function-autoscaler): publish a Cassandra 0.17.2-compatible image

[sbaum1994]

Describe the bug

The latest published function-autoscaler image, 1.21.0, is incompatible with Cassandra migrations 0.17.2. The migrations drop nvcf_autoscaler.recently_invoked_functions_history, but image 1.21.0 still writes to that table. An all observability profile can install successfully and report healthy while scale-from-zero never creates an instance.

The autoscaler source on main has already removed the obsolete history writes, but no compatible semantic-versioned image has been published from that source revision.

Steps or code to reproduce bug

1. Install the self-managed stack with Cassandra migrations 0.17.2.
2. Enable the function autoscaler with image 1.21.0.
3. Deploy a function with zero minimum instances and invoke it.
4. Observe the autoscaler discover the recently invoked function.
5. Observe function discovery fail because recently_invoked_functions_history does not exist.
6. Observe no ICMSRequest or worker instance is created.

Expected behavior

A function-autoscaler image compatible with migrations 0.17.2 should be published and used by the self-managed stack. Release validation should prevent a migrations pin from advancing past the latest published autoscaler schema contract.

Additional context

This was reproduced in the local TestObservabilityAll BDD after the control and compute stacks were healthy. The existing source changes that remove obsolete Cassandra state are newer than the 1.21.0 image tag.

Related: #1553 retained the older migrations pin because no compatible autoscaler image was available at that time.

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