scRNAseq - reduce the second session to 1.5/2 hours

[ayushi-agrawal-gladstone]

• [x] Use sctransform in the demo instead of log normalize, find variable features and scale data
• [x] Remove TSNE steps from demo
• [x] Remove the TSNE notebook from hands-on materials
• [ ] Include a merge step in demo; visualize metadata to show how to look for batch effects
• [x] Mention in pre-workshop instructions email that the slides might be changed (similar to the email for Intro to RNA-seq)
• [ ] A slide on publicly available data, how to access it and how to clean it up (maybe share a script for clean up?)

[ayushi-agrawal-gladstone]

@MichelaTr @reubenthomas Maybe we can have some time for installation errors (related to all demos) at the end of session 1 and cover some of the topics in session 2?