chore(deps): Bump jenkins/ssh-agent in /dockerfiles/maven

Bumps jenkins/ssh-agent from 5.17.0 to 5.20.0.

---
updated-dependencies:
- dependency-name: jenkins/ssh-agent
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

dockerfiles/maven/Dockerfile

@@ -1,4 +1,4 @@
-FROM jenkins/ssh-agent:5.17.0 as ssh-agent
+FROM jenkins/ssh-agent:5.20.0 as ssh-agent
 
 # ca-certificates because curl will need it later on for the maven installation
 RUN apt-get update && apt-get install -y --no-install-recommends ca-certificates curl && apt-get clean && \