Update both vale and markdownlint

It has been a while since we updated the linters. Vale has been moving along with a fair amount of updates, and the latest version fixes a bug Evan reported, so I think now is a good time to update: https://github.com/errata-ai/vale/tags

Same for markdownlint, which has made minor improvements to some of the rules that we use: https://github.com/DavidAnson/markdownlint#history (version number is from markdownlint-cli, which is slightly different than the node project, but does not have a changelog).