Fix HB 1.7.1

[palmskog]

cc: @gares

[erikmd]

@palmskog @gares what was the incentive of this upper bound?

FYI, this broke the following build:

https://gitlab.inria.fr/math-comp/docker-mathcomp/-/jobs/5183944#L406

while coq-mathcomp-character built fine before this PR:

https://gitlab.inria.fr/math-comp/docker-mathcomp/-/jobs/5165018#L412

[palmskog]

@erikmd it was to fix crashes with Coq-Elpi 2.4, which as the latest stable version was getting installed. You can see the same fix for HB 1.8 here: #3294

[palmskog]

@erikmd from what I can tell, the build you are referring to (https://gitlab.inria.fr/math-comp/docker-mathcomp/-/jobs/5183944#L406) is actually broken because of the combination of HB 1.7.1 and Coq-Elpi 2.4.0, which is ruled out by this PR.

[erikmd]

@palmskog OK!

Thanks for your answer, and apologies for skimming the PR and not realizing earlier that it specifically addressed the issue, not the other way around!

So, I restarted the build and I confirm that the correct dependencies were picked then!

https://gitlab.inria.fr/math-comp/docker-mathcomp/-/jobs/5194087

Thanks