Clicking on some links lead nowhere

[CohenCyril]

e.g. clicking on copy in

points to
https://math-comp.github.io/analysis/htmldoc_1_7_0/mathcomp.analysis.lebesgue_integral.html#copy
which is not a valid anchor.

This might be related to LPCIC/coq-elpi#575

CC @gares @affeldt-aist

[affeldt-aist]

This might be the same issue as #12

[yoshihiro503]

This is same as #144