Bugfix: Bump up Polaris to 5.1.0 in Examples to Fix Broken Builds

[harismh]

WHY are these changes introduced?

Fixes #3334 using the dependency version from #3130

WHAT is this pull request doing?

Fresh builds of the create-react-app and create-react-app-ts examples were broken and yielded the following error:

Failed to compile.

./node_modules/@shopify/polaris/dist/styles.css (./node_modules/css-loader/dist/cjs.js??ref--6-oneOf-3-1!./node_modules/postcss-loader/src??postcss!./node_modules/@shopify/polaris/dist/styles.css)
Error: Cannot find module '@shopify/browserslist-config'
    at Array.reduce (<anonymous>)

Bumping up @shopify/polaris from 5.0.0 to 5.1.0 resolves this. At the suggestion of @BPScott, all of the example apps were synced and their yarn.locks were rebuilt. All example builds are working now.

Summary of the changes committed

• Run yarn in the repository root
• Bump up Polaris to 5.1.0 in examples/create-react-app, /create-react-app-ts-react-testing, /next-js, and /webpack.
• Run yarn and rebuild yarn.lock in examples
• Test new builds locally

[ghost]

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[BPScott]

Fantastic, thank you for doing this for us!

[ghost]

🎉 Thanks for your contribution to Polaris React!