Incorrect input data for srna tutorial

Hi @malloryfreeberg

One of the .eu users ran the [Differential abundance testing of small RNAs](https://training.galaxyproject.org/training-material/topics/transcriptomics/tutorials/srna/tutorial.html) and encountered some issues with the tutorial. :/

> In the Hands on after FastQC it is said that the datasets should have adapters (picture attached from the hands-on). But the output we got shows no adapters and also TrimGalore was unable to trim reads?

@wm75 reproduced the report and noted that the data uploaded to zenodo is already trimmed. Do you potentially have the dataset for the step before that? Otherwise we'll have to find someone to rewrite the tutorial to remove this step.

Lastly a minor issue, the "Zenodo" link in [here](https://training.galaxyproject.org/training-material/topics/transcriptomics/tutorials/srna/tutorial.html#data-upload-and-organization) points to the wrong record.

Start with the Differential abundance testing of small RNAs tutorial, especially the FastQC and TrimGalore hands-on steps and the Data upload and organization section. Verify whether the Zenodo data is already trimmed, then resolve the adapter-processing instructions and correct the Zenodo link; the tutorial should accurately describe the supplied input data.

Written by the indexing model from the issue text.