Broken hover style of some dropdowns

The following discussion from !30477 (merged) should be addressed:

• @winh started a discussion: (+4 comments)

  I think this rule is still too specific. Can we avoid the :not() here?

  Some dropdown hover styles are still broken, for example:

  

  Replacing this lines with just

  -   button:not(.dropdown-toggle,.ci-action-icon-container),
  +   button,

  seems to fix it.