Update repository image for gitea postgresql to use appropriate image and tag

Gitea helm chart relies on Bitnami images for postgresql.

Beginning August 28th, 2025, Bitnami evolved its public catalog to offer
a curated set of hardened, security-focused images under the new Bitnami
Secure Images initiative. As part of this transition, starting August 28th,
all existing container images, including older or versioned tags have been
migrated from the public catalog (docker.io/bitnami) to the "Bitnami Legacy"
repository (docker.io/bitnamilegacy), where they will no longer receive updates.

Reference:
https://github.com/bitnami/charts/tree/main/bitnami/postgresql



Change-Id: I2f46ee434178ea31eb1fa23cfa44c47afb3931db
Signed-off-by: garciadeblas <gerardo.garciadeblas@telefonica.com>