x11-terms/terminus-bin: fix icon cache update

inheriting xdg will automatically export the correct
things to the correct phases, no need to set anything
manually

Closes: https://bugs.gentoo.org/783813
Package-Manager: Portage-3.0.18, Repoman-3.0.3
Signed-off-by: Andrew Ammerlaan <andrewammerlaan@riseup.net>

x11-terms/terminus-bin/terminus-bin-1.0.137.ebuild

@@ -60,7 +60,3 @@ src_install(){
 		doicon -s "${i}" ../terminus-"${i}".png
 	done
 }
-
-pkg_postinst(){
-	xdg_desktop_database_update
-}