Hotfix v0.10.6

Version 0.10.6

• Qt6 support:
  • Handled all occurences of deprecated QWidget.getContentsMargins method.
  • Removed references to NonCosmeticDefaultPen
  • Fixed QApplication.desktop AttributeError
  • Fixed QPrinter.HighResolution AttributeError on Linux
  • Fixed QPrinter.setColorMode AttributeError on PyQt6/Linux
  • Fixed QPrinter.setOrientation deprecation issue
  • Fixed QPrinter.setPaperSize deprecation issue
• Improved unit tests:
  • Ensure that tests are entirely executed before quitting (in unattended mode)
  • Added more tests on qwt.symbols
  • Added tests on qwt.plot_renderer
• qwt.plot_renderer: fixed resolution type
• qwt.symbols: fixed QPointF type mismatch
• Removed CHM help file generation (obsolete)