fix(Checkbox): specify a font size for the checked glyph

[booc0mtaco]

Specify a font-size for the glyph in the checkbox so that wrapping adjacent text doesn't change the size of the glyph when :checked

Test Plan:

Before:

After:

• [ ] Wrote/updated automated tests
• [ ] CI tests / new tests are not applicable
• [ ] Manually tested my changes, and here are the details:

[github-actions[bot]]

size-limit report 📦

Path	Size
components	89.26 KB (0%)
styles	27.68 KB (+0.13% 🔺)

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 97.43%. Comparing base (2ad7b4c) to head (4c93c92).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## next #2030 +/- ## ======================================= Coverage 97.43% 97.43% ======================================= Files 109 109 Lines 2608 2608 Branches 664 664 ======================================= Hits 2541 2541 Misses 65 65 Partials 2 2 ```

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