Update deprecated ::shadow selector

[vinkla]

Starting from Atom v1.13.0, the contents of atom-text-editor elements are no longer encapsulated within a shadow DOM boundary. This means you should stop using :host and ::shadow pseudo-selectors, and prepend all your syntax selectors with syntax--. To prevent breakage with existing style sheets, Atom will automatically upgrade the following selectors:

• atom-text-editor::shadow .ecfg-wrap-guide => atom-text-editor.editor .ecfg-wrap-guide

Automatic translation of selectors will be removed in a few release cycles to minimize startup time. Please, make sure to upgrade the above selectors as soon as possible.

[florianb]

Thank you @vinkla 💝 - will release this as soon as possible.