Swap "git" variant to be "dind"-based in 23+

Historically, `docker build git://...` would invoke `git` in the client context, but `buildx` does so in the daemon context instead, and given that it is the default in 23+, let's adjust the git-including variant to be dind-based to simplify this for users who desire the 50MiB+ increase this workflow requires.

Author: tianon

23.0/git/Dockerfile

@@ -1,3 +1,3 @@
-FROM docker:{{ env.version }}-cli
+FROM docker:{{ env.version }}-{{ if env.version | rtrimstr("-rc") == "20.10" then "cli" else "dind" end }}
 
 RUN apk add --no-cache git