Merge pull request hashicorp#6854 from mootpt/doc-fix-artifacts

Update artifact.html.markdown

Author: jen20

website/source/docs/providers/atlas/r/artifact.html.markdown

@@ -53,7 +53,8 @@ The following arguments are supported:
   to find a matching artifact in the latest build, "any" to find a
   matching artifact in any build, or a specific number to pin to that
   build. If `build` and `version` are unspecified, `version` will default
-  to "latest". Cannot be specified with `version`.
+  to "latest". Cannot be specified with `version`. Note: `build` is only 
+  present if Atlas builds the image.
 
 * `version` - (Optional)  The version of the artifact to filter on. This can
   be "latest", to match against the latest version, "any" to find a matching artifact