Pin ANTLR version (#1061)

Author: munozemilio

packages/lu/package.json

@@ -36,7 +36,7 @@
     "@azure/cognitiveservices-luis-authoring": "4.0.0-preview.1",
     "@azure/ms-rest-azure-js": "2.0.1",
     "@types/node-fetch": "~2.5.5",
-    "antlr4": "^4.7.2",
+    "antlr4": "~4.8.0",
     "chalk": "2.4.1",
     "console-stream": "^0.1.1",
     "deep-equal": "^1.0.1",