fix: PG 15 backups working by default

[yajo]

Problem description

In 30b6124 this update was forgotten. It is needed for logical backups of postgres 15 clusters, as seen in #1945 (comment).

The default value documented is different to the one actually used:

postgres-operator/docs/reference/operator_parameters.md

Lines 753 to 758 in 9973262

	* **logical_backup_docker_image**
	An image for pods of the logical backup job. The [example image](https://github.com/zalando/postgres-operator/blob/master/docker/logical-backup/Dockerfile)
	runs `pg_dumpall` on a replica if possible and uploads compressed results to
	an S3 bucket under the key `/spilo/pg_cluster_name/cluster_k8s_uuid/logical_backups`.
	The default image is the same image built with the Zalando-internal CI
	pipeline. Default: "registry.opensource.zalan.do/acid/logical-backup:v1.9.0"

Linked issues

Fixes #1945.

@moduon MT-1075

Checklist

Thanks for submitting a pull request to the Postgres Operator project.
Please, ensure your contribution matches the following items:

• Your go code is formatted. Your IDE should do it automatically for you.
• You have updated generated code when introducing new fields to the acid.zalan.do api package.
• New configuration options are reflected in CRD validation, helm charts and sample manifests.
• New functionality is covered by unit and/or e2e tests.
• You have checked existing open PRs for possible overlay and referenced them.

[FxKu]

👍

[jopadi]

👍

[FxKu]

Thanks @yajo. It will be bumped once again for the next release anyway - but a good reminder to not forget it again.