download the correct Ricin icon

Author: SkyzohKey

appimage.sh

@@ -37,7 +37,7 @@ find . -name *desktop -exec cp {} $LOWERAPP.desktop \;
 sed -i -e 's|Ricin|ricin|g' $LOWERAPP.desktop
 sed -i -e 's|.svg||g' $LOWERAPP.desktop
 
-wget https://raw.githubusercontent.com/RicinApp/ricin.im/master/static/images/apple-touch-icon.png -O $LOWERAPP.png ### FIXME
+wget https://cdn.ricin.im/images/ricin-icon-plain.svg -O $LOWERAPP.svg
 
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 # Copy in the dependencies that cannot be assumed to be available