Doc: Make links explicitly require C++ targets


This prevents QDoc from choosing QML targets for QSignalTransition in
some cases.

Change-Id: I6e783a970fd5a784c0fffefc0e24ef1cd5c0ba51
Reviewed-by: Ulf Hermann <ulf.hermann@qt.io>
commit3b1bee546c35409e8d0355a13a9afd9b88a640d3
parent293b6fa71bce935135a5d68601389136fc1c5051
authorDavid Boddie <david.boddie@qt.io>
committerDavid Boddie <david.boddie@qt.io>
commit timeTue, 8 Sep 2026 10:24:23 +0000