Update dependency ava to v6

Author: renovate[bot]

package.json

@@ -42,7 +42,7 @@
     "@babel/polyfill": "7.12.1",
     "@babel/preset-env": "7.13.10",
     "@babel/register": "7.13.8",
-    "ava": "3.15.0",
+    "ava": "6.3.0",
     "coveralls": "3.1.0",
     "esdoc": "1.1.0",
     "esdoc-inject-script-plugin": "1.0.0",