Use Node 22.12.0 LTS instead of unstable 23.x

Author: mikemaccana

.github/workflows/test.yml

@@ -21,7 +21,7 @@ jobs:
           arcium-version: "0.5.4"
           solana-cli-version: "2.3.11"
           anchor-version: "0.32.1"
-          node-version: "23.6.0"
+          node-version: "22.12.0"
 
       # Override with Arcium 0.6.2 binary
       # arcup 0.6.2 has bootstrap bug (panics with "index not found" at arcup/src/config.rs:29:51)