Infrastructure: Bump ava from 3.14.0 to 3.15.0 (pull #1713)

Bumps [ava](https://github.com/avajs/ava) from 3.14.0 to 3.15.0.
- [Release notes](https://github.com/avajs/ava/releases)
- [Commits](avajs/ava@v3.14.0...v3.15.0)

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

package.json

@@ -32,7 +32,7 @@
  },
  "homepage": "https://github.com/w3c/aria-practices#readme",
  "devDependencies": {
- "ava": "^3.14.0",
+ "ava": "^3.15.0",
  "cheerio": "^1.0.0-rc.5",
  "cspell": "^5.1.3",
  "eslint": "^7.17.0",