Fix link to Appendix A

[flamableconcrete]

I noticed the link to the appendix was broken, so I fixed it!

[MikeRalphson]

Thanks. May though be related to #1726 if there were actual broken links in the spec, mdv should have spotted them (bugs are always possible).

[MikeRalphson]

If this does turn out to be necessary, we'll probably ask you to resubmit it against the v3.0.3-dev branch and to the versions/3.0.3.md file.

[flamableconcrete]

Yeah, that definitely looks related. I'll close this pull request in favor of that issue being addressed

[MikeRalphson]

Thanks.