Reorder and trim normalization lesson

[nsohail19]

Reorder the normalization and regression lesson so that it follows this order with:

• simple normalization
• highly variable genes
• ScaleData() - make this separate from the HighlyVariableFeatures() function call
• PCA - show pca split by sample
• Calculate cell cycle score and show on PCA
• SCTransform

Will also need to minimize the amount of text/explanations because it is too long to fit into the 4 day schedule.