fix: remove unused upstream.postgresql.primary.securityContext

[tumido]

Description of the change

upstream.postgresql.primary.securityContext doesn't exist in upstream bitnami/postgresql chart anymore. Let's clean it up here.

https://github.com/search?q=repo%3Abitnami%2Fcharts%20path%3A%2F%5Ebitnami%5C%2Fpostgresql%5C%2F%2F%20securityContext&type=code

Existing or Associated Issue(s)

Additional Information

Checklist

• Chart version bumped in Chart.yaml according to semver.
• Variables are documented in the values.yaml and added to the README.md. The pre-commit utility can be used to generate the necessary content. Use pre-commit run -a to apply changes.
• JSON Schema template updated and re-generated the raw schema via pre-commit hook.
• List tests pass for Chart using the Chart Testing tool and the ct lint command.

[schwesig]

Code is looking good IMHO
Note: it is hitting an error against Test Latest Release, but that is expected.
latest is still 0.2. The next image refers to 1.0