Bump postcss-parser-tests from 6.5.0 to 8.3.0

Bumps [postcss-parser-tests](https://github.com/postcss/postcss-parser-tests) from 6.5.0 to 8.3.0.
- [Release notes](https://github.com/postcss/postcss-parser-tests/releases)
- [Changelog](https://github.com/postcss/postcss-parser-tests/blob/master/CHANGELOG.md)
- [Commits](postcss/postcss-parser-tests@6.5.0...8.3.0)

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

package-lock.json

@@ -97,7 +97,7 @@
     "np": "^6.5.0",
     "npm-run-all": "^4.1.5",
     "postcss": ">=7.0.32",
-    "postcss-parser-tests": "^6.5.0",
+    "postcss-parser-tests": "^8.3.0",
     "postcss-safe-parser": "^4.0.2",
     "postcss-syntax": ">=0.36.2",
     "prettier": "^2.1.1",