update node version in buildscript.txt

services/docstore/buildscript.txt

@@ -1,6 +1,6 @@
 docstore
 --language=coffeescript
---node-version=6.14.1
+--node-version=10.19.0
 --acceptance-creds=aws
 --dependencies=mongo,redis
 --docker-repos=gcr.io/overleaf-ops