misc/qtchooser: remove

QtChooser allows you to select your version of Qt among those installed.
However, this tool is no longer supported upstream and will not be
available for Qt6.
By default, our Qt installations are done in
${LOCALBASE}/lib/qt${QT_VERSION} as recommended.

We have added symbolic linking for the main binaries to
${LOCALBASE}/bin with the suffix -qt5.