Update libtest-mimic requirement from 0.7.0 to 0.8.1 #2952

Job	Run time
Check (stable)	2m 17s
Check (nightly)	1m 11s
Check Documentation	1m 4s
List directories for parallelizing tests	2s
Test (stable)	9m 24s
Check Style	4s
Test (nightly)	17m 35s
Test assembly	8m 18s
Test (cp6_782/)	28m 57s
Test (mnt4_753/)	15m 10s
Test (mnt6_753/)	34m 42s
Check no_std	31s
Test (./mnt6_298)	5m 28s
Test (./ed_on_bls12_381)	1m 13s
Test (./ed_on_cp6_782)	1m 16s
Test (./ed_on_bw6_761)	37s
Test (./ed_on_bn254)	59s
Test (./ed25519)	54s
Test (./secp384r1)	1m 16s
Test (./bw6_761)	3m 48s
Test (./bn254)	2m 18s
Test (./ed_on_bls12_377)	1m 3s
Test (./bw6_767)	4m 2s
Test (./bls12_381)	3m 31s
Test (./bls12_377)	4m 13s
Test (./curve25519)	1m 5s
Test (./secp256r1)	53s
Test (./grumpkin)	1m 8s
Test (./ed_on_mnt4_753)	3m 47s
Test (./secp256k1)	1m 7s
Test (./vesta)	1m 6s
Test (./ed_on_mnt4_298)	1m 8s
Test (./pallas)	1m 5s
Test (./secq256k1)	1m 2s
Test (./ed_on_bls12_381_bandersnatch)	1m 2s
Test (./mnt4_298)	3m 55s
	2h 47m 11s

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