Remove suffix from Icon key in desktop entries

Suffixes, like .png, are not part of the specification. Although many
ports like misc/xfce4-appfinder have implemented workarounds for it,
ports like x11/rofi are missing icons due to a suffix being present in the
Icon key.

References:
- https://specifications.freedesktop.org/desktop-entry-spec/latest/ar01s06.html
- https://specifications.freedesktop.org/icon-theme-spec/icon-theme-spec-latest.html#icon_lookup

Approved by:	portmgr (blanket, runtime fixes)

net/remotebox/Makefile

@@ -3,7 +3,7 @@
 
 PORTNAME=	remotebox
 DISTVERSION=	2.5
-PORTREVISION=	1
+PORTREVISION=	2
 CATEGORIES=	net
 MASTER_SITES=	http://remotebox.knobgoblin.org.uk/downloads/
 DISTNAME=	RemoteBox-${DISTVERSION}

net/remotebox/files/remotebox.desktop

@@ -5,6 +5,6 @@ Type=Application
 Name=Remotebox
 GenericName=Remotebox
 Comment=Open Source VirtualBox Client with Remote Management
-Icon=remotebox.png
+Icon=remotebox
 Exec=remotebox
 Categories=System

x11/gcb/Makefile

@@ -3,7 +3,7 @@
 
 PORTNAME=	gcb
 PORTVERSION=	0.2.8
-PORTREVISION=	8
+PORTREVISION=	9
 CATEGORIES=	x11
 MASTER_SITES=	http://freebsd.flatrate.ru/distfiles/ \
 		http://ccbsd9.csie.nctu.edu.tw/~cp76/gcb/

x11/gcb/files/gcb.desktop

@@ -2,7 +2,7 @@
 Encoding=UTF-8
 Name=Gtk Copy-paste Buffer
 Comment=A GTK+ tool for managing x11 cut-buffers
-Icon=gcb.png
+Icon=gcb
 Exec=gcb -B
 Type=Application
 Categories=GNOME;Application;System