Replace outdated polyfill.io link in FAQ

[dev2820]

Description
This PR updates the polyfill.io reference in the FAQ section. The polyfill.io domain has been involved in a supply chain attack and is no longer maintained. This change replaces it with a safer alternative (polyfill-fastly.io).

Issue
N/A

Example

Context

Checks

• The new code matches the existing patterns and styles.
• The tests pass with yarn test.
• The linter passes with yarn lint. (Fix errors with yarn fix.)
• The relevant examples still work. (Run examples with yarn start.)
• You've added a changeset if changing functionality. (Add one with yarn changeset add.)

[changeset-bot]

⚠️ No Changeset found

Latest commit: 016cfbd

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

This PR includes no changesets

When changesets are added to this PR, you'll see the packages that this PR includes changesets for and the associated semver types

Click here to learn what changesets are, and how to add one.

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