Save 28786 bytes of disk space by removing unneeded metadata from two
PNG files.

Bug: 991654
Change-Id: I6b29592501c2cd6737c392e146f0770464453855
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1742609Reviewed-by: Mike West <mkwst@chromium.org>
Commit-Queue: Eric Lawrence [MSFT] <ericlaw@microsoft.com>
Cr-Commit-Position: refs/heads/master@{#685528}