Update libtest-mimic requirement from 0.7.0 to 0.8.1 (#860) #2955

Job	Run time
Check no_std	2m 37s
Check Documentation	57s
Check (stable)	9s
List directories for parallelizing tests	8s
Check (nightly)	1m 13s
Check Style	5s
Test (stable)	9m 14s
Test assembly	8m 19s
Test (nightly)	17m 44s
Test (cp6_782/)	10s
Test (mnt4_753/)	14m 37s
Test (mnt6_753/)	21m 19s
Test (./ed_on_mnt4_753)	4m 10s
Test (./secp256r1)	57s
Test (./ed_on_mnt4_298)	1m 4s
Test (./ed_on_cp6_782)	1m 26s
Test (./mnt4_298)	3m 47s
Test (./mnt6_298)	5m 26s
Test (./ed_on_bn254)	1m 6s
Test (./bn254)	2m 28s
Test (./secp256k1)	1m 11s
Test (./bw6_761)	4m 3s
Test (./bls12_377)	4m 17s
Test (./grumpkin)	1m 9s
Test (./secp384r1)	1m 24s
Test (./ed_on_bls12_377)	1m 15s
Test (./secq256k1)	53s
Test (./ed25519)	53s
Test (./ed_on_bls12_381)	1m 16s
Test (./ed_on_bw6_761)	47s
Test (./curve25519)	1m 23s
Test (./ed_on_bls12_381_bandersnatch)	1m 11s
Test (./pallas)	1m 12s
Test (./vesta)	1m 8s
Test (./bw6_767)	4m 7s
Test (./bls12_381)	3m 15s
	2h 6m 20s

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