ci: pin Node.js 22.x to 22.6 due to Node.js buffer issue

Needs to be pinned until nodejs/node#54518 is
resolved.

Other references:
* protobufjs/protobuf.js#2025
* protobufjs/protobuf.js#2026

Author: basti1302

.github/workflows/verify.yaml

@@ -14,7 +14,7 @@ jobs:
 
     strategy:
       matrix:
-        node-version: [ '18.x',  '20.x', '21.x', '22.x' ]
+        node-version: [ '18.x',  '20.x', '21.x', '22.6' ]
 
     steps:
       - uses: actions/checkout@v4