fix(Select): move selected from <option> to defaultValue on <select>

[joshblack]

We currently set selected on the <option> within a <select> when placeholder is provided. When doing so, we receive the following error from styled-components:

Warning: Use the `defaultValue` or `value` props on <select> instead of setting `selected` on <option>.
    at option
    at select
    at StyledComponent (/Users/joshblack/gh/primer/react/node_modules/styled-components/dist/styled-components.cjs.js:1950:5)
    at Select__StyledSelect
    at span
    at StyledComponent (/Users/joshblack/gh/primer/react/node_modules/styled-components/dist/styled-components.cjs.js:1950:5)
    at _TextInputWrapper__TextInputWrapper
    at block (/Users/joshblack/gh/primer/react/src/Select.tsx:67:5)

This PR removes the selected prop from <option> and instead optionally specifies the defaultValue if placeholder is present.

Note
When a consumer passes in defaultValue, it should continue to override whatever is provided since {...rest} is applied after defaultValue

[changeset-bot]

🦋 Changeset detected

Latest commit: aeac346

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

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

[github-actions]

size-limit report 📦

Path	Size
dist/browser.esm.js	78.82 KB (+0.01% 🔺)
dist/browser.umd.js	79.47 KB (+0.01% 🔺)

[josepmartins]

🚀