Update manual.tex: Fixed way of importing autosubst #28

Job	Run time
build (mathcomp/mathcomp-dev:coq-dev)	2m 56s
build (mathcomp/mathcomp:2.2.0-coq-8.19)	3m 6s
build (mathcomp/mathcomp:2.1.0-coq-8.18)	3m 2s
build (mathcomp/mathcomp:2.0.0-coq-8.17)	3m 6s
build (mathcomp/mathcomp:1.17.0-coq-8.17)	2m 57s
build (mathcomp/mathcomp:1.16.0-coq-8.17)	3m 5s
build (mathcomp/mathcomp:1.15.0-coq-8.16)	16m 24s
build (mathcomp/mathcomp:1.14.0-coq-8.15)	3m 7s
build (mathcomp/mathcomp:1.13.0-coq-8.15)	3m 6s
build (mathcomp/mathcomp:1.12.0-coq-8.14)	3m 4s
	43m 53s

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