Minor source compatibility break in QLoggingCategory

A change made to QLoggingCategory between Qt 6.2.3 and Qt 6.5.1 caused code that used the API as seen below, to no longer compile.

QLoggingCategory logging functions, like qCDebug, qCInfo, qCWarning, allowed passing a function returning a reference to a declared category as argument:

Q_LOGGING_CATEGORY(category, "mycat", QtInfoMsg)
...
QLoggingCategory &cat() { return category; }
...
qCInfo(cat) << "Info";