net: openthread: cleanup diag commands #156010

Job	Run time
twister-build-prep / prep_pr	4m 44s
twister-build-prep / prep_push	0s
twister-build (1)	32m 53s
twister-build (2)	30m 3s
twister-build (3)	26m 42s
twister-build (4)	42m 33s
twister-build (5)	23m 18s
twister-build (6)	21m 16s
twister-build (7)	31m 14s
Publish Unit Tests Results	12s
Check Twister Status / all jobs passed	1s
	3h 32m 56s

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