fix(item): use the correct highlight for an inset line input item

[brandyscarney]

The code to make inset highlight work was removed by this commit: fd79b57#diff-be35bd653745acb6d128c4ec32dd2e6fL172

This PR adds the code back which makes the highlight work again, but I'm not sure why it was removed in the first place.

Pull request checklist

Please check if your PR fulfills the following requirements:

• Tests for the changes have been added (for bug fixes / features)
• Docs have been reviewed and added / updated if needed (for bug fixes / features)
• Build (npm run build) was run locally and any changes were pushed
• Lint (npm run lint) has passed locally and any fixes were made for failures

Pull request type

Please check the type of change your PR introduces:

• Bugfix
• Feature
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no api changes)
• Build related changes
• Documentation content changes
• Other (please describe):

What is the current behavior?

The inset highlight is taking up the full width

Issue Number: #18051

What is the new behavior?

The inset highlight has left padding to match the item border.

Does this introduce a breaking change?

• Yes
• No

Other information