Limit requests to 2.9 for LinkChecker
Limit requests to 2.9 for LinkChecker

It incorrectly inspects the version of 2.10+ and thinks it is
lower than 2.2.

See: https://github.com/wummel/linkchecker/issues/649

mkdocs/mkdocs,mkdocs/mkdocs,waylan/mkdocs,d0ugal/mkdocs,pjbull/mkdocs,pjbull/mkdocs,d0ugal/mkdocs,jimporter/mkdocs,d0ugal/mkdocs,jimporter/mkdocs,lukfor/mkdocs,pjbull/mkdocs,waylan/mkdocs,waylan/mkdocs,lukfor/mkdocs,lukfor/mkdocs,mkdocs/mkdocs,jimporter/mkdocs