chore: update CI node version matrix to remove deprecated version 18

Author: rossarmstrong

.github/workflows/ci.yml

@@ -11,7 +11,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        node: [18, 20, 22]
+        node: [20, 22]
     steps:
       - uses: actions/checkout@v4
       - uses: actions/setup-node@v4