fix(core/modal): border-radius value

[goncalosard]

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 (yarn build) was run locally and any changes were pushed
• Unit tests (yarn test) were run locally and passed
• Visual Regression Tests (yarn visual-regression) were run locally and passed
• Linting (npm lint) was run locally and passed

Pull request type

Please check the type of change your PR introduces:

• Bug fix
• Feature
• Refactoring (no functional changes, no API changes)
• Build related changes
• Documentation content changes
• Other (please describe):

What is the current behavior?

GitHub Issue Number: #509

What is the new behavior?

• Changed border-radius value to correct value from Figma

Does this introduce a breaking change?

• Yes
• No

Testing

Other information

[danielleroux]

We should also try to improve the visual regression test first, because the test has to fail without updating the image refs.

Maybe it is necessary to adapt the screenshot target area to reduce the compared pixel ratio.