[kcmkwin] Use new icons for virtual desktops, touch screen, and screen edges KCMs

Summary: New icons were added in D18483 and D18490, so this is 5.16 only.

Test Plan: {F6565234, size=full}

Reviewers: #vdg, #plasma, ndavis

Reviewed By: #vdg, ndavis

Subscribers: kwin

Tags: #kwin

Differential Revision: https://phabricator.kde.org/D18492

kcmkwin/kwindesktop/kcm_kwin_virtualdesktops.desktop

@@ -1,6 +1,6 @@
 [Desktop Entry]
 Exec=kcmshell5 kcm_kwin_virtualdesktops
-Icon=preferences-desktop
+Icon=preferences-desktop-virtual
 Type=Service
 X-KDE-ServiceTypes=KCModule
 X-DocPath=kcontrol/kwin_virtualdesktops/index.html

kcmkwin/kwinscreenedges/kwinscreenedges.desktop

@@ -1,6 +1,6 @@
 [Desktop Entry]
 Exec=kcmshell5 kwinscreenedges
-Icon=preferences-desktop
+Icon=preferences-desktop-gestures-screenedges
 Type=Service
 X-KDE-ServiceTypes=KCModule
 X-DocPath=kcontrol/kwinscreenedges/index.html

kcmkwin/kwinscreenedges/kwintouchscreen.desktop

@@ -1,6 +1,6 @@
 [Desktop Entry]
 Exec=kcmshell5 kwintouchscreen
-Icon=preferences-desktop
+Icon=preferences-desktop-gestures-touch
 Type=Service
 X-KDE-ServiceTypes=KCModule