Update health check paths

[subigre]

WireMock has a system endpoint that can be used to return the health status of the server.
It doesn’t change a lot, but I think it makes "a bit more sense" to use this operation for liveness and readiness probes instead of the current /__admin/mappings

https://wiremock.org/docs/standalone/admin-api-reference/#tag/System/operation/getHealth

References

n/a

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[gitkent]

LGTM - Thanks for your contribution.