[7.x] [docs/getting-started] link to yarn v1 specifically (#76169) (#76200)

Co-authored-by: spalger <spalger@users.noreply.github.com>

Co-authored-by: spalger <spalger@users.noreply.github.com>

Author: Spencer

docs/developer/getting-started/index.asciidoc

@@ -30,7 +30,7 @@ you can switch to the correct version when using nvm by running:
 nvm use
 ----
 
-Install the latest version of https://yarnpkg.com[yarn].
+Install the latest version of https://classic.yarnpkg.com/en/docs/install[yarn v1].
 
 Bootstrap {kib} and install all the dependencies: