chore(deps): bump ajv from 6.12.0 to 6.12.6

Bumps [ajv](https://github.com/ajv-validator/ajv) from 6.12.0 to 6.12.6.
- [Release notes](https://github.com/ajv-validator/ajv/releases)
- [Commits](ajv-validator/ajv@v6.12.0...v6.12.6)

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

package.json

@@ -53,7 +53,7 @@
   "homepage": "https://www.fff-badminton.de/#/dashboard",
   "optionalDependencies": {
     "@types/markerclustererplus": "2.1.33",
-    "ajv": "6.12.0",
+    "ajv": "6.12.6",
     "typescript": "4.2.3"
   },
   "devDependencies": {