Remove package validation suite from Project (#4146)

Project/Packages/manifest.json

     "com.unity.ml-agents": "file:../../com.unity.ml-agents",
     "com.unity.ml-agents.extensions": "file:../../com.unity.ml-agents.extensions",
     "com.unity.package-manager-ui": "2.0.8",
-    "com.unity.package-validation-suite": "0.7.15-preview",
     "com.unity.purchasing": "2.0.3",
     "com.unity.textmeshpro": "1.4.1",
     "com.unity.modules.ai": "1.0.0",