submodule: bump third_party/openthread/repo from `025d84b` to `ada03e6` #6637

Job	Run time
docker-check	4m 4s
buildx (latest, ubuntu:bionic, linux/amd64,linux/arm/v7,linux/arm64, yes)	30m 54s
buildx (focal, ubuntu:focal, linux/amd64,linux/arm64, yes)	22m 58s
buildx (jammy, ubuntu:jammy, linux/amd64,linux/arm64, yes)	20m 54s
buildx (reference-device, ubuntu:bionic, --build-arg REFERENCE_DEVICE=1 --build-arg BORDER_ROUTIN...	27m 58s
buildx (test, ubuntu:bionic, --build-arg OT_BACKBONE_CI=1 --build-arg REFERENCE_DEVICE=1 --build-...	32m 12s
	2h 19m 0s

Provide feedback