[ResultDB] Add link to ResultDB concepts doc
[ResultDB] Add link to ResultDB concepts doc

Add go/resultdb-concepts in the recipe_module as the reference for ResultDB data.

Change-Id: Ic243accf4174b4bb5f8922fd6c55e82eefbad73b
Reviewed-on: https://chromium-review.googlesource.com/c/infra/luci/recipes-py/+/2174826
Commit-Queue: Chan Li <332b6c56634d0f63001046c664a2370006a02420@chromium.org>
Commit-Queue: Nodir Turakulov <ef4933a197ef7b4b3f55f1bec4942aead3637a2a@chromium.org>
Auto-Submit: Chan Li <332b6c56634d0f63001046c664a2370006a02420@chromium.org>
Reviewed-by: Nodir Turakulov <ef4933a197ef7b4b3f55f1bec4942aead3637a2a@chromium.org>

luci/recipes-py,luci/recipes-py