#11599 Fix API reference link

[twm]

Scope and purpose

Use an intersphinx-style link rather than an absolute one so that the generated link is relative.

You can see the result here:

The monospace formatting is unfortunate but such is Sphinx. 🤷

Fixes #11599.

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[exarkun]

Thanks! Great to have this link fixed.

[exarkun]

Note - I enabled auto-merge.