CMake Property Reference: duplicate anchors

https://doc.qt.io/qt-6/cmake-property-reference.html: there are three subsections "Source File Properties" with the same anchor, source-file-properties. This means that https://doc.qt.io/qt-6/cmake-property-reference.html#source-file-properties refers to three sections (three <h3 id="source-file-properties">), but the browser can only point to the first one.

I'm not entirely sure how this file is generated, which is why I'm not offering any patch.

Fix: there are three <h3 id="source-file-properties">, there should be none: there should always be a disambiguator in the ID, something like <h3 id="source-file-properties-qtcore">, <h3 id="source-file-properties-qtdbus">, and <h3 id="source-file-properties-qtqml">.

The same problems happens with global-properties.