Revert "Optimize all SVGs"

On my Mac, calling finfo_file on external-link-ltr-icon.svg gets the correct
MIME-type ("image/svg+xml"), but in production I get  "application/xml".
This is probably due to the version of fileinfo or libmagic that is deployed on
the cluster. Reverting for now.

This reverts commit a9b855eea52ba3b739a9150beb8e69db8afd2143.

Change-Id: Ie4db624ba9f561a467622878d0992847be018b7d
(cherry picked from commit 472c27f8ca146fcb60da7c4e474e29c368b6a8d0)