Docs seem misleading about necessity of Firefox for exporting plots

Per Exporting plots — Bokeh 2.4.2 Documentation, following the “install with conda” and “selenium and geckodriver” options, there appears to be no need to install Firefox at all. One could just run conda install selenium geckodriver -c conda-forge and things would be fine.

However, Firefox does need to be on the system, whether it’s there via conda install firefox -c conda-forge or via some other method.

I had thought that using conda install selenium geckodriver -c conda-forge would be all that’s needed, so I wasted some time before I figured this out.

The docs should be updated to reflect this, correct? I’m happy to put in a pull request if this sounds right.

@efremdan1 PRs to improve documentation are always welcome