Core: Removed env.elements for 'before-highlightall'

[RunDevelopment]

This removes the env.elements property from the environment of the before-highlightall hook.

Why?

• There is no plugin that is using it.
• It is inherently incompatible with env.selector. Even if a plugin using elements wanted to respect selector it would not be able to because 1) there might be plugins after it (in before-highlightall) extending the selector and 2) the plugin has no access to the current container.

Isn't this a breaking change?
Yes, but I don't think that this will have any impact for the above reasons and because from a user perspective, it's hard to use than just iteration over your elements and calling Prism.highlightElement yourself.

[mAAdhaTTah]

I'm ok with this. I doubt anyone is using this for real.