build: pin Node 21.x to minor

Co-authored-by: Aravind Nair <22199259+aravindvnair99@users.noreply.github.com>

Author: UlisesGascon

appveyor.yml

@@ -22,7 +22,7 @@ environment:
     - nodejs_version: "18.19"
     - nodejs_version: "19.9"
     - nodejs_version: "20.11"
-    - nodejs_version: "21.6.2"
+    - nodejs_version: "21.6"
 cache:
   - node_modules
 install: