fix: In event processor, reverted back the typescript version to fix stubbing issue (#531)

Summary:

Typescript version was updated which resulted in some problems with stubbing event processor. Reverted back to the version which was being used earlier.

Test plan:

Tested by locally linking this version of event processor with optimizely sdk and verified that stubbing works correctly after this fix.

Author: zashraf1985

packages/event-processor/package-lock.json

@@ -49,7 +49,7 @@
     "jest": "^23.6.0",
     "jest-localstorage-mock": "^2.4.0",
     "ts-jest": "^23.10.5",
-    "typescript": "^3.3.3333"
+    "typescript": "3.3.3333"
   },
   "peerDependencies": {
     "@react-native-community/netinfo": "5.9.4",