Drop duplicate $btn-close-focus-shadow definition

[julien-deramond]

Description

Drop duplicate definition of $btn-close-focus-shadow:

bootstrap/scss/_variables.scss

Lines 1694 to 1696 in 2dc329d

	$btn-close-focus-shadow: $input-btn-focus-box-shadow !default;
	$btn-close-bg: url("data:image/svg+xml,<svg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 16 16' fill='#{$btn-close-color}'><path d='M.293.293a1 1 0 0 1 1.414 0L8 6.586 14.293.293a1 1 0 1 1 1.414 1.414L9.414 8l6.293 6.293a1 1 0 0 1-1.414 1.414L8 9.414l-6.293 6.293a1 1 0 0 1-1.414-1.414L6.586 8 .293 1.707a1 1 0 0 1 0-1.414z'/></svg>") !default;
	$btn-close-focus-shadow: $focus-ring-box-shadow !default;

Type of changes

• Enhancement (non-breaking change)

Checklist

• I have read the contributing guidelines
• My code follows the code style of the project (using npm run lint)
• (N/A) My change introduces changes to the documentation
• (N/A) I have updated the documentation accordingly
• (N/A) I have added tests to cover my changes
• All new and existing tests passed

[mdo]

Whoops :D