Bump node from 18.17-alpine to 18.18-alpine in /silta-node/18-alpine

Bumps node from 18.17-alpine to 18.18-alpine.

---
updated-dependencies:
- dependency-name: node
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

silta-node/18-alpine/Dockerfile

@@ -1,4 +1,4 @@
-FROM node:18.17-alpine
+FROM node:18.18-alpine
 
 RUN apk add --no-cache openssh bash rsync curl