bump ajv from 6.12.6 to 7.2.1 (#150)

Bumps [ajv](https://github.com/ajv-validator/ajv) from 6.12.6 to 7.2.1.
- [Release notes](https://github.com/ajv-validator/ajv/releases)
- [Commits](ajv-validator/ajv@v6.12.6...v7.2.1)

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

package.json

@@ -50,7 +50,7 @@
     "clean": "rm -rf node_modules && rm -f package-lock.json && npm install"
   },
   "devDependencies": {
-    "ajv": "^6.12.4",
+    "ajv": "^7.2.1",
     "appium-gulp-plugins": "^5.3.2",
     "babel-eslint": "^10.1.0",
     "chai": "^4.2.0",