Temporarily replace AppImage icon

The AppImage specification states that .DirIcon must be a PNG.
Currently, it's a PNG inside of an SVG container. This is the only place
where this file is used I believe.

The png was taken from `src/Ryujinx/Ryujinx.ico`. I believe there is
plans to replace the icon anyway. This also makes the icon consistent
with Windows and MacOS (it was smaller and had background shadows)

Hopefully this should also stop the SVG from randomly showing up in
searches on the forgejo. That may have been the reason I started looking
into this.

distribution/linux/appimage/build-appimage.sh

@@ -14,9 +14,9 @@ cp -r "$BUILDDIR"/* AppDir/usr/lib/
 
 cp distribution/linux/appimage/app.ryujinx.Ryujinx.appdata.xml AppDir/usr/share/metainfo/app.ryujinx.Ryujinx.appdata.xml
 cp distribution/linux/app.ryujinx.Ryujinx.desktop AppDir/app.ryujinx.Ryujinx.desktop
-cp distribution/misc/Logo.svg AppDir/app.ryujinx.Ryujinx.svg
+cp distribution/misc/Logo.png AppDir/app.ryujinx.Ryujinx.png
 
-ln -s ./app.ryujinx.Ryujinx.svg AppDir/.DirIcon  # Must be png, swap out later
+ln -s ./app.ryujinx.Ryujinx.png AppDir/.DirIcon
 ln -s ../lib/Ryujinx AppDir/usr/bin/Ryujinx
 ln -s ./usr/lib/Ryujinx.sh AppDir/AppRun