chore(deps): update mariadb docker tag to v20.5.3 (#55)

This PR contains the following updates:

| Package | Update | Change |
|---|---|---|
| [mariadb](https://redirect.github.com/bitnami/charts)
([source](https://redirect.github.com/bitnami/charts/tree/HEAD/bitnami/mariadb))
| minor | `20.4.3` -> `20.5.3` |

---

### Release Notes

<details>
<summary>bitnami/charts (mariadb)</summary>

###
[`v20.5.3`](https://redirect.github.com/bitnami/charts/blob/HEAD/bitnami/mariadb/CHANGELOG.md#2053-2025-04-24)

- adds spec.terminationGracePeriodSeconds to mariadb
([#&#8203;33168](https://redirect.github.com/bitnami/charts/pull/33168))

</details>

---

### Configuration

📅 **Schedule**: Branch creation - At any time (no schedule defined),
Automerge - At any time (no schedule defined).

🚦 **Automerge**: Enabled.

♻ **Rebasing**: Whenever PR is behind base branch, or you tick the
rebase/retry checkbox.

🔕 **Ignore**: Close this PR and you won't be reminded about this update
again.

---

- [ ] <!-- rebase-check -->If you want to rebase/retry this PR, check
this box

---

This PR was generated by [Mend Renovate](https://mend.io/renovate/).
View the [repository job
log](https://developer.mend.io/github/jeboehm/mailserver-charts).

<!--renovate-debug:eyJjcmVhdGVkSW5WZXIiOiIzOS4yNTcuMyIsInVwZGF0ZWRJblZlciI6IjM5LjI1Ny4zIiwidGFyZ2V0QnJhbmNoIjoibWFpbiIsImxhYmVscyI6W119-->

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

charts/docker-mailserver/Chart.yaml

@@ -24,7 +24,7 @@ dependencies:
   repository: oci://registry-1.docker.io/bitnamicharts
   condition: redis.enabled
 - name: mariadb
-  version: 20.4.3
+  version: 20.5.3
   repository: oci://registry-1.docker.io/bitnamicharts
   condition: mariadb.enabled
 - name: common