Update batch image export tutorial link

client tutorials in the main docs have been replaced by the 'help' guides for some time but this script was still pointing at a link which doesn't exist anymore.
merge dev_5_0 -D org: PR 86 (Update batch image export tutorial link (rebased onto dev_5_0))
merge dev_5_0 -D org

Repository: ome/scripts
Already up-to-date.

Merged PRs:
  # PR 86 sbesson 'Update batch image export tutorial link (rebased onto dev_5_0)'
Generated by OMERO-5.0-merge-push#72 (http://ci.openmicroscopy.org/job/OMERO-5.0-merge-push/72/)