Update METADATA to link to upstream project am: 2e54c35cfe am: 68d5fa8757 am: 5c4eb6637b

Original change: https://android-review.googlesource.com/c/platform/external/libmpeg2/+/2475549

Change-Id: Ic20f67458ad55aed5ef57ef199f60acec5073d07
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>