Update third_party/kernel to point to main branches instead of release. BUG=None TEST=repo init and sync RELEASE_NOTE=None Change-Id: I8d21a6248ff1c80c3deca250b2bc09b08c14860a Reviewed-on: https://cos-review.googlesource.com/c/cos/manifest/+/35647 Reviewed-by: Arnav Kansal <rnv@google.com> Tested-by: Meena Shanmugam <meenashanmugam@google.com>