Change ref-based RNA-seq tutorial to use fastqsanger.gz instead of fastqsanger files

In the ref-based RNA-seq tutorial (here: http://galaxyproject.github.io/training-material/topics/transcriptomics/tutorials/ref-based/tutorial.html#data-upload) uncompressed fastq files are currently used as input but it would be better to use compressed fastqs because:
1) it would save on storage/quotas
2) compressed files are more common in real-world analyses

Requires replacing the fastqsanger files in Zenodo (here: https://zenodo.org/record/1185122) with fastqsanger.gz versions.