[FIX] doc: Sphinx 1.2 support in html_domain

9a07a459 added "override=True" to silence a Sphinx warning in about
the address node already existing, however the override=True parameter
was added in Sphinx 1.4 (alongside the warning), so this breaks in
1.2.

Only pass in override=True if we're in 1.4 or later.

Closes #18232