Fixes for Qt 6

[data-man]

[leozide]

What errors are you getting? Everything was compiling fine for me when I tested Qt6.

[data-man]

qt/lc_renderdialog.cpp:225:9: error: 'QRegExp' was not declared in this scope
  225 |         QRegExp RegexPovRayProgress("Rendered (\\d+) of (\\d+) pixels.*");
      |         ^~~~~~~
qt/lc_renderdialog.cpp:226:9: error: 'RegexPovRayProgress' was not declared in this scope
  226 |         RegexPovRayProgress.setCaseSensitivity(Qt::CaseInsensitive);