Revert version bump of rdkafka dep

Author: TiMESPLiNTER

pkg/rdkafka/composer.json

@@ -7,7 +7,7 @@
     "license": "MIT",
     "require": {
         "php": "^7.1.3",
-        "ext-rdkafka": "^3.1.0",
+        "ext-rdkafka": "^3.0.3",
         "queue-interop/queue-interop": "^0.7|^0.8"
     },
     "require-dev": {