update buildscript.txt to node 10.21.0

services/spelling/buildscript.txt

@@ -6,6 +6,6 @@ spelling
 --env-add=
 --env-pass-through=
 --language=es
---node-version=10.19.0
+--node-version=10.21.0
 --public-repo=False
 --script-version=2.0.0