docs: add Envoy expose path configurability to changelog

[shoenig]

For when

• connect: enable proxy.expose configuration #7323 (needs approval)
• connect: enable automatic expose paths for TG service checks #7515 (done)
• docs: add documentation for proxy.expose configuration #7440 (needs approval)
  are complete.

[shoenig]

On second thought, the path stanza page probably does not need to exist, and can just be provided as a lower section of the expose page (similar to how checks is a sub-section of service).

Updated the docs to reflect the per-check design in #7515

[shoenig]

This is in, minus the docs PR

[github-actions]

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