docs: fix two links pointing at non-existent same-page anchors

[v1teka]

configuration.md linked cd() to #cd, but cd() is documented in api.md. api.md linked ProcessOutput to #processoutput, but ProcessOutput has its own page, process-output.md, which the same file already links to elsewhere.

Fixes #issue / suggests an improvement

import {$} from 'zx'

• Setup Set the latest Node.js LTS version.
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• Docs: I’ve added or updated relevant documentation as needed.
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