chore(deps): update node docker tag to v21 (dockerfile)

Dockerfile

@@ -7,7 +7,7 @@
 # docker tag hello-world-rest:local cloudkats/hello-world-rest:local
 # docker push cloudkats/hello-world-rest:local
 ###
-FROM node:18-alpine@sha256:c7620fdecfefb96813da62519897808775230386f4c8482e972e37b8b18cb460
+FROM node:21-alpine@sha256:c986eb0b8970240f8d648e524bab46016b78f290f912aac16a4aa6705dde05f4
 
 # Create app directory
 WORKDIR /usr/src/app