Trim versions list?

[bryevdv]

Our version switcher is getting a bit long:

Can/should we trim this on the 3.7 release? What versions should we drop? e.g. personally I'd say we can drop 3.1 to 3.3 but should we still keep the 2.4.3 for now as well?

cc @bokeh/dev

[mattpap]

I think it should be fine to keep 3~4 versions of the current major version and one of the previous. I would definitely keep one version of 2.x branch, because it looks like it still has a lot a lot of users (based on discussions and bug reports).