x11: Don't force QT_NO_GLIB=1

This breaks certain apps, e.g. KDE System Settings when launched from
overview effect.

BUG: 460980

src/main_x11.cpp

@@ -342,10 +342,6 @@ int main(int argc, char *argv[])
 
     signal(SIGPIPE, SIG_IGN);
 
-    // Disable the glib event loop integration, since it seems to be responsible
-    // for several bug reports about high CPU usage (bug #239963)
-    setenv("QT_NO_GLIB", "1", true);
-
     // enforce xcb plugin, unfortunately command line switch has precedence
     setenv("QT_QPA_PLATFORM", "xcb", true);