Don't set QT_SCREEN_SCALE_FACTORS on wayland

Summary:
Scale factor is sent on the output, we don't need to have the hacky env
variables.

When the kscreen KCM is used on wayland it doesn't set the variable this
is using.

Test Plan:
Configured an X session to have high DPI with this variable.
Logged into a wayland session, ran env.

(font DPI is still a problem, if it gets set on X
 it's visually doubled on my wayland session. )

Reviewers: #plasma

Subscribers: plasma-devel

Tags: #plasma

Differential Revision: https://phabricator.kde.org/D7781

startkde/startplasmacompositor.cmake

@@ -31,7 +31,6 @@ kcminputrc Mouse cursorTheme 'breeze_cursors'
 kcminputrc Mouse cursorSize ''
 ksplashrc KSplash Theme Breeze
 ksplashrc KSplash Engine KSplashQML
-kdeglobals KScreen ScaleFactor 1
 kcmfonts General forceFontDPI 0
 EOF
 
@@ -101,15 +100,10 @@ if test $returncode -ne 0; then
 fi
 [ -r $configDir/startupconfig ] && . $configDir/startupconfig
 
-if [ $kdeglobals_kscreen_scalefactor -gt 1 ]; then
-    export QT_SCREEN_SCALE_FACTORS="$kdeglobals_kscreen_scalefactor"
-fi
 #Manually disable auto scaling because we are scaling above
-#otherwise apps that manually opt in for high DPI get auto scaled by the developer AND manually scaled by us
+#otherwise apps that manually opt in for high DPI get auto scaled by the developer AND scaled by the wl_output
 export QT_AUTO_SCREEN_SCALE_FACTOR=0
 
-
-
 # XCursor mouse theme needs to be applied here to work even for kded or ksmserver
 if test -n "$kcminputrc_mouse_cursortheme" -o -n "$kcminputrc_mouse_cursorsize" ; then
     @EXPORT_XCURSOR_PATH@