Fixup: minor error with pyGenomeTracks option in workflow for atac-seq

[jennaj]

https://training.galaxyproject.org/training-material/topics/epigenetics/tutorials/atac-seq/tutorial.html

This is the single bad option. If fixed-up, tutorial's entire wf runs great at ORG :)

ping @lldelisle @mblue9 @heylf

[lldelisle]

Hi,
It is not a typo. In the tutorial it is written:

But as this error arises really often we should put a box on how to solve the issue.
Like:
If you get an error, please check that the ENCFF933NTR.bed.gz has been changed to encodepeak.