Fix `verify-doc-links` on CI
Clarification and motivation
verify-doc-links CI job currently reports some errors. We should fix them somehow.
I think that https://gitlab.com/morley-framework/morley/-/issues/new should be ignored because this link is good, but
xrefcheck doesn't like it most likely because it requires authorization. So we need https://github.com/serokell/xrefcheck/pull/53
xrefcheck doesn't report any errors on CI.