chore: update AVA to work with Node.js 18

[nickytonline]

Thanks for contributing the Netlify plugins directory!

Are you adding a plugin or updating one?

This unblocks an issue AVA has with Node.js 18. This will unblock #813

• Adding a plugin
• Updating a plugin
• updating testing infrastructure

Have you completed the following?

• Read and followed the plugin author guidelines.
• Included all required fields in your entry.
• Tested the plugin locally and on Netlify, using the plugin version stated in your entry.

Test plan
All tests should pass as no changes to plugins have been made.

See:

• Node.js 18.8.0 changed return type of module.findSourceMap() nodejs/node#44391
• https://github.com/avajs/ava/releases/tag/v4.3.3