Update 2018 project version to fix burst errors. (#4977)

Project/Packages/manifest.json

     "com.unity.collab-proxy": "1.2.15",
     "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.purchasing": "2.0.3",
+    "com.unity.package-manager-ui": "2.0.13",
+    "com.unity.purchasing": "2.2.1",
     "com.unity.textmeshpro": "1.4.1",
     "com.unity.modules.ai": "1.0.0",
     "com.unity.modules.animation": "1.0.0",

Project/ProjectSettings/ProjectVersion.txt

-m_EditorVersion: 2018.4.24f1
+m_EditorVersion: 2018.4.32f1