Remove Node 18 from CI, add Node 24

Node 18 has been EoL for a year. Also, dev deps sinon 19+, chai 5+, and sinon-chai 4+ require at least Node 20, since require(esm) was only backported as far back as Node 20 - https://joyeecheung.github.io/blog/2025/12/30/require-esm-in-node-js-from-experiment-to-stability/\#Backporting-require-esm-to-v22-and-v20-LTS

Author: ericyhwang

.github/workflows/test.yml

@@ -17,9 +17,9 @@ jobs:
     strategy:
       matrix:
         node:
-        - 18
         - 20
         - 22
+        - 24
     services:
       mongodb:
         image: mongo:4.4