A minor follow-up/addendum to PR #199: after further testing, setting this attribute to True globally seems to produce no ill consequences on GNU/Linux on low-resolution displays (but keeping it set to False when the QT_SCALE_FACTOR env var is 2 or greater results in "blocky" pixmaps).

Note that this change does not address the issue(s) described in #198: Qt's AA_EnableHighDpiScaling is broken on Qubes-OS and does nothing to upscale window-sizes in conjunction with GNOME's display scale setting (at least on a 1080p display).