remove ajv (import-jdl workaround for jhipster v7.0.0)

Author: ruddell

package.json

@@ -49,7 +49,6 @@
     ]
   },
   "dependencies": {
-    "ajv": "7.2.4",
     "chalk": "4.1.0",
     "fs-extra": "9.1.0",
     "generator-jhipster": "7.0.1",