Update dependency ava to v3.15.0

Author: renovate-bot

package.json

@@ -84,7 +84,7 @@
     "@babel/core": "7.11.6",
     "@babel/preset-env": "7.11.5",
     "@babel/register": "7.11.5",
-    "ava": "3.12.1",
+    "ava": "3.15.0",
     "babel-plugin-transform-remove-console": "6.9.4",
     "babel-plugin-unassert": "3.0.1",
     "babel-preset-power-assert": "3.0.0",