submodule: bump third_party/openthread/repo from `3ae741f` to `7bd3abd` #5431

Job	Run time
Border Router (mDNSResponder)	28m 10s
Border Router (Avahi)	27m 29s
Border Router TREL (mDNSResponder)	30m 2s
Border Router TREL (Avahi)	30m 8s
Border Router MATN (mDNSResponder)	17m 28s
Border Router Internet Access Features (mDNSResponder)	21m 56s
Backbone Router	15m 49s
Border Router TREL with FEATURE_FLAG (avahi)	28m 4s
	3h 19m 6s

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