Fix iteration order in the rasterizer script (#676)

Summary:
The initial logo checkin in #637 included the 32px raster image, but
generated it in the _wrong order_ in the rasterizer script. This commit
fixes that heinous bug once and for all.

Test Plan:
Running `rasterize.sh` does not change the output.

wchargin-branch: rasterize-32px

src/assets/logo/rasterize.sh

@@ -3,7 +3,7 @@ set -eu
 
 main() {
     cd "$(dirname "$0")"
-    for size in 1024 512 256 128 32 64 16; do
+    for size in 1024 512 256 128 64 32 16; do
         rasterize "${size}"
     done
 }