Make podman-compose refer to podman-compose(1) when using an external provider

[marinmo]

This PR is meant to fix https://github.com/containers/podman/issues/22904. It makes the warning message emitted by podman-compose when using an external provider point to podman-compose(1) which is also updated to include instructions on how to disable said message.

Does this PR introduce a user-facing change?

Changed the warning message emitted by `podman-compose` when using an external compose provider. Instead of referring to "the documentation" it now refers to the man page of `podman-compose(1)` which is also updated to contain the relevant information.

[openshift-ci[bot]]

Adding the "do-not-merge/release-note-label-needed" label because no release-note block was detected, please follow our release note process to remove it.

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[openshift-ci[bot]]

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[marinmo]

Seems the build is failing due to tests which really shouldn't be necessary for a man page? Please lmk if any further action is required on my part.