Bootstrap 4.1.2 `.close` hover focus styles are too specific

Created by: pat270

https://github.com/twbs/bootstrap/commit/4f1bb98587411d6db16783ea116ff6d5d8f8fa49 from 4.1.2 moved hover focus styles on the .close component into &:not(:disabled):not(.disabled) making it too specific. This breaks hover focus states for those that extended the close component from previous versions.

https://github.com/twbs/bootstrap/commit/eb5d0b49dc7439fa1cc3d0c41406eef00de149c1 makes it a little better, but the problem is still there.