Retire PreloadDefaultIsMetadata runtime enabled flag.

Feature was enabled by default in M64. Flag isn't required anymore.

Bug: 310450
Change-Id: I5e6bd409ad9fc874cd2e9401e10707be9af1e6a8
Reviewed-on: https://chromium-review.googlesource.com/c/1324136
Reviewed-by: Mounir Lamouri <mlamouri@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Commit-Queue: Dave Tapuska <dtapuska@chromium.org>
Cr-Commit-Position: refs/heads/master@{#606508}
4 files changed