bigenough dependency for mathcomp-analysis and mathcomp-finmap

[palmskog]

It looks like the package coq-mathcomp-finmap introduced the following dependency for version 1.2.0:

"coq-mathcomp-bigenough" { (>= "1.0.0" & < "1.1.0~") }

However, as far as I can see, this dependency is not used by coq-mathcomp-finmap itself, in all versions up to and including the most recent one, 1.4.0.

Nevertheless, the package coq-mathcomp-analysis depends on coq-mathcomp-finmap and on coq-mathcomp-bigenough - but only the former dependency is explicitly listed in, e.g., coq-mathcomp-analysis.0.2.3.

It's probably a good idea to refactor the various OPAM package versions to reflect these dependency relationships.

cc: @anton-trunov @CohenCyril