Restore doctrine/orm requirement, add 3

Author: andrewmy

composer.json

@@ -26,7 +26,7 @@
     "psr/container": "^1.1 || ^2.0",
     "makasim/temp-file": "^0.2",
     "google/cloud-pubsub": "^1.46",
-    "doctrine/orm": "3.6.x-dev",
+    "doctrine/orm": "^2.12|^3.5",
     "doctrine/persistence": "^2.0|^3.0|^4.0",
     "mongodb/mongodb": "^1.17",
     "pda/pheanstalk": "^3.1",