Do not return directories as "unmapped" resources in d2d pipelines

[pombredanne]

We should not return directories as "unmapped" resources in d2d pipelines. This is noise.

[tdruez]

@pombredanne A pipe to flag directories is already part of the pipeline steps, see https://github.com/aboutcode-org/scancode.io/blob/main/scanpipe/pipelines/deploy_to_develop.py#L271
For some reason, this may be bypassed in your case, but we need you to provide more context about the inputs used and the enabled options to debug why some directories are returned as "unmapped".