Bump postgres from 15.3 to 16.1 in /postgres

Bumps postgres from 15.3 to 16.1.

---
updated-dependencies:
- dependency-name: postgres
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

postgres/Dockerfile

@@ -1,4 +1,4 @@
-FROM postgres:15.3
+FROM postgres:16.1
 
 ENV POSTGRES_USER=sampleUser
 ENV POSTGRES_PASSWORD=openliberty