fix: update protobuf version to 25.2

fixes #63 / #33 

works OOB with MacOS aarch64. 

26.x/27.x fail on MacOS aarch64 for integrations with via pact_ffi for

- php
- swift
- dotnet
- lua

pact-plugin.json

@@ -6,7 +6,7 @@
   "executableType": "exec",
   "entryPoint": "pact-protobuf-plugin",
   "pluginConfig": {
-    "protocVersion": "21.12",
+    "protocVersion": "25.2",
     "downloadUrl": "https://github.com/protocolbuffers/protobuf/releases/download",
     "hostToBindTo": "127.0.0.1"
   }