Updated the .workspace selector
Updated the .workspace selector

I replaced the deprecated '.workspace' selector with the new 'atom-workspace' selector to fix the following deprecation error:

"Use the `atom-workspace` tag instead of the `workspace` class."

https://atom.io/docs/v0.149.0/upgrading/upgrading-your-ui-theme
surdu/selector-to-tag,surdu/selector-to-tag