Omit colorbar in embedding plots

[asistradition]

• Additional function parameters / changed functionality / changed defaults?
• New analysis tool: A simple analysis tool you have been using and are missing in sc.tools?
• New plotting function: A kind of plot you would like to seein sc.pl?
• External tools: Do you know an existing package that should go into sc.external.*?
• Other?

Categorical legends can be removed from embedding plots by passing the argument 'none' to legend_loc (e.g. sc.pp.umap(adata, color="CellType", legend_loc='none').

It would be useful if the drawn colorbar is omitted when plotting continuous data if legend_loc='none' is passed.

[ivirshup]

Fixed by #1821