qt: do not initialize unused qt quick effects shaders

As per Qt Quick Effects' CMakeLists.txt [1], the excluded resources are the ones that use masking.

We do not use mask, so we don't need to initialize these shaders. This should save some disk space for the static build.

We could eliminate more of these, for example depending on the blur level, only a certain subset of these shaders are used. However, I decided to not be that aggressive for the moment.

[1] https://github.com/qt/qtdeclarative/blob/6.8.2/src/effects/CMakeLists.txt#L68

Request review @chub.