Bump ajv from 5.5.2 to 6.12.3

Bumps [ajv](https://github.com/ajv-validator/ajv) from 5.5.2 to 6.12.3.
- [Release notes](https://github.com/ajv-validator/ajv/releases)
- [Commits](ajv-validator/ajv@v5.5.2...v6.12.3)

---
updated-dependencies:
- dependency-name: ajv
  dependency-type: direct:development
...

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

package.json

@@ -39,7 +39,7 @@
     "@wdio/mocha-framework": "^7.5.2",
     "@wdio/spec-reporter": "^7.5.2",
     "@wdio/sync": "^7.5.2",
-    "ajv": "5.5.2",
+    "ajv": "6.12.3",
     "babel-loader": "^8.0.5",
     "body-parser": "^1.19.0",
     "chai": "^4.2.0",