Add subtle border to the avatar to match the CSS implementation

[maximedegreve]

The avatar was missing a border compared to the css implementation.

The change is best visible in dark modes with @colebemis's avatar.

<Avatar src="https://avatars.githubusercontent.com/u/4608155?s=100&v=4" size={50} />

Merge checklist

• Added/updated tests
• Added/updated documentation
• Tested in Chrome
• Tested in Firefox
• Tested in Safari
• Tested in Edge

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[changeset-bot]

🦋 Changeset detected

Latest commit: bc7b85a

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@primer/react	Patch

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[github-actions]

size-limit report 📦

Path	Size
dist/browser.esm.js	76.32 KB (+0.02% 🔺)
dist/browser.umd.js	76.93 KB (+0.02% 🔺)

[siddharthkp]

Hi!

Do you have access to the chromatic build to make sure all the visual changes are intentional: https://www.chromatic.com/build?appId=61a90feace7802003a4d9c45&number=1009

Side note: In case you want, you can review all the different themes at once now: https://primer-6e414db3be-13348165.drafts.github.io/storybook/?path=/story/tokens-avatartoken--default-token&globals=colorScheme:all

Side note 2: You might need to update jest snapshots by running npm run test:update

[maximedegreve]

Hey @siddharthkp

I forgot about Chromatic, it's so good! 🥹 The visual changes look good.

I've tried to update the snapshots but I got into an error:

[siddharthkp]

I'm not 100% sure, but I think running npm install and npm build before updating snapshots should fix this