try restricting test workflow to node 18

Author: mkbehr

.github/workflows/ci.yaml

@@ -32,7 +32,7 @@ jobs:
 
     strategy:
       matrix:
-        node-version: [18.x, 20.x, 22.x]
+        node-version: [18.x]
 
     steps:
     - uses: actions/checkout@v4