Minor variables scss cleanup ($btn-focus-box-shadow)

Created by: 719media

Prerequisites

• I have searched for duplicate or closed issues
• I have validated any HTML to avoid common problems
• I have read the contributing guidelines

Describe the issue

there is a variable in use $btn-focus-box-shadow that looks like its only use is just to be used as default for $accordion-button-focus-box-shadow seems like probably should just remove the singular instance use of $btn-focus-box-shadow and replace it with the much more widely used $input-btn-focus-box-shadow

Reduced test cases

No test case, just a variable cleanup

What operating system(s) are you seeing the problem on?

Linux

What browser(s) are you seeing the problem on?

No response

What version of Bootstrap are you using?

v5.2.0