[v0.12] ci(docs-upstream): pin reusable workflow

[crazy-max]

follow-up #2210 (comment)
related to docker/docs#19220

need to pin docs validate upstream workflow to a commit with artifact v3 support as this is not backward compat with v4 from main.

[crazy-max]

workflow looks to fail and seems related to new uri for ref docs:

#28 [validate-upstream 5/5] RUN htmltest
#28 0.059 htmltest started at 09:17:12 on public
#28 0.059 ========================================================================
#28 7.267 engine/reference/commandline/buildx_build/index.html
#28 7.267   hash does not exist --- engine/reference/commandline/buildx_build/index.html --> /engine/reference/commandline/build/#build-arg
#28 7.267 ========================================================================
#28 10.27 ✘✘✘ failed in 10.210694744s
#28 10.27 1 errors in 2088 documents

@dvdksn Do we miss a backport?

Edit: Ah this one I guess #2186