Update flix-tech/avro (#67)

* Update flix-tech/avro
* Bump avro version to 4.3

Author: tPl0ch

composer.json

@@ -18,7 +18,7 @@
     "guzzlehttp/promises": "^1.4.0",
     "guzzlehttp/psr7": "^1.7|^2.1",
     "beberlei/assert": "~2.7|~3.0",
-    "flix-tech/avro-php": "^4.1"
+    "flix-tech/avro-php": "^4.3"
   },
   "require-dev": {
     "phpunit/phpunit": "^9.4.2",