chore(deps): update ghcr.io/jeboehm/fetchmailmgr docker tag to v0.3.21 (#83)

This PR contains the following updates:

| Package | Update | Change |
|---|---|---|
|
[ghcr.io/jeboehm/fetchmailmgr](https://redirect.github.com/jeboehm/fetchmailmgr)
| patch | `0.3.18` -> `0.3.21` |

---

### Release Notes

<details>
<summary>jeboehm/fetchmailmgr (ghcr.io/jeboehm/fetchmailmgr)</summary>

###
[`v0.3.21`](https://redirect.github.com/jeboehm/fetchmailmgr/releases/tag/v0.3.21)

[Compare
Source](https://redirect.github.com/jeboehm/fetchmailmgr/compare/v0.3.20...v0.3.21)

#####
[0.3.21](https://redirect.github.com/jeboehm/fetchmailmgr/compare/v0.3.20...v0.3.21)
(2025-08-25)

###
[`v0.3.20`](https://redirect.github.com/jeboehm/fetchmailmgr/releases/tag/v0.3.20)

[Compare
Source](https://redirect.github.com/jeboehm/fetchmailmgr/compare/v0.3.19...v0.3.20)

#####
[0.3.20](https://redirect.github.com/jeboehm/fetchmailmgr/compare/v0.3.19...v0.3.20)
(2025-08-18)

###
[`v0.3.19`](https://redirect.github.com/jeboehm/fetchmailmgr/releases/tag/v0.3.19)

[Compare
Source](https://redirect.github.com/jeboehm/fetchmailmgr/compare/v0.3.18...v0.3.19)

#####
[0.3.19](https://redirect.github.com/jeboehm/fetchmailmgr/compare/v0.3.18...v0.3.19)
(2025-08-11)

</details>

---

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---

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---

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charts/docker-mailserver/values.yaml

@@ -1295,7 +1295,7 @@ fetchmail:
   image:
     registry: ghcr.io
     repository: jeboehm/fetchmailmgr
-    tag: 0.3.18@sha256:a007d58e45491da9c9598874ae7914708c8a87ab8e7a3d18d5cf8ccd25b1eb52
+    tag: 0.3.21@sha256:26c4691b28a4d97f55fb3c4b4d1331478f9c1966d2d351293d7b8071f26e0654
     ## Specify a imagePullPolicy
     ## ref: https://kubernetes.io/docs/concepts/containers/images/#pre-pulled-images
     ##