Remove Not Disabled Selectors on Buttons

What does this MR do?

Removes unneeded :not(:disabled):not(.disabled) selectors from outline buttons, as it seems unnecessary and is causing specificity errors.

disabled_buttons

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Code review guidelines
• Style guides

Performance and testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers