desktopToDarwinBundle: Drop 48x48 size

On macOS 10.13 the 48x48 icon size is not supported. It results in a
corrupted image being displayed. I suspect the image data is being
truncated to what it expects for 32x32 or maybe data is read for
128x128, which would be a buffer overflow.

pkgs/build-support/setup-hooks/desktop-to-darwin-bundle.sh

@@ -18,7 +18,9 @@ convertIconTheme() {
     local -r iconName=$3
     local -r theme=${4:-hicolor}
 
-    local -ra iconSizes=(16 32 48 128 256 512)
+    # Sizes based on archived Apple documentation:
+    # https://developer.apple.com/design/human-interface-guidelines/macos/icons-and-images/app-icon#app-icon-sizes
+    local -ra iconSizes=(16 32 128 256 512)
     local -ra scales=([1]="" [2]="@2")
 
     # Based loosely on the algorithm at:
@@ -31,13 +33,6 @@ convertIconTheme() {
         local scaleSuffix=${scales[$scale]}
         local exactSize=${iconSize}x${iconSize}${scaleSuffix}
 
-        if [[ $exactSize = '48x48@2' ]]; then
-            # macOS does not support a 2x scale variant of 48x48 icons
-            # See: https://en.wikipedia.org/wiki/Apple_Icon_Image_format#Icon_types
-            echo "unsupported"
-            return 0
-        fi
-
         local -a validSizes=(
             ${exactSize}
             $((iconSize + 1))x$((iconSize + 1))${scaleSuffix}