[CI:DOCS] docs: correct default authfile path

[rhatdan]

What type of PR is this?

/kind api-change
/kind bug
/kind cleanup
/kind deprecation
/kind design
/kind documentation
/kind failing-test
/kind feature
/kind flake
/kind other

What this PR does / why we need it:

How to verify it

Which issue(s) this PR fixes:

Special notes for your reviewer:

Does this PR introduce a user-facing change?

None

Replaces #5294

[rhatdan]

@flouthoc @nalind @vrothberg @ashley-cui @wulfgarpro PTAL

[wulfgarpro]

@rhatdan, auth.json is stored at /run/containers/0/auth.json when rootful.

[vrothberg]

I prefer pointing to man containers-auth.json instead?

[rhatdan]

Modified to point at man page.

[flouthoc]

LGTM

[openshift-ci]

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[nalind]

/lgtm