Build(deps): bump tiredofit/db-backup in /docker/backup

Bumps tiredofit/db-backup from 4.1.15 to 4.1.16.

---
updated-dependencies:
- dependency-name: tiredofit/db-backup
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

docker/backup/Dockerfile

@@ -1,4 +1,4 @@
-FROM tiredofit/db-backup:4.1.15
+FROM tiredofit/db-backup:4.1.16
 LABEL maintainer="Ozren Dabić (dabico@usi.ch)"
 
 RUN apk update --quiet && \