Update Axon Framework link in prior-art docs

[Copilot]

The prior-art.md page still referenced the retired axonframework.org domain, which causes link checking to hang on spine.io. This updates the Axon reference to the current AxonIQ Framework URL.

• Problem

  • Replace the stale Axon Framework link in the prior art section with the current canonical destination.

• Change

  • Updated the Markdown link in docs/content/docs/introduction/prior-art.md:
    • http://www.axonframework.org/
    • → https://www.axoniq.io/axon-framework

• Result

  • Removes a dead/timeout-prone external reference from the docs.
  • Keeps the existing content unchanged apart from the target URL.

products and solutions like [Axon](https://www.axoniq.io/axon-framework), [Spring](https://spring.io/), [Kurrent](https://www.kurrent.io/)

[alexander-yevsyukov]

LGTM