Link to WASI spec on https://webassembly.org/specs/ is dead

[DianaNites]

A PR 3 weeks ago in the WASI repo, WebAssembly/WASI#510, seems to have broken the link because the file was moved from https://github.com/WebAssembly/WASI/blob/master/phases/snapshot/docs.md to https://github.com/WebAssembly/WASI/blob/main/legacy/preview1/docs.md

[tomayac]

This was fixed out-of-bounds since. Closing.