chore(deps): update gomods/athens docker tag to v0.15.4 (#94)

This PR contains the following updates:

| Package | Update | Change |
|---|---|---|
| [gomods/athens](https://redirect.github.com/gomods/athens) | patch |
`v0.15.3` -> `v0.15.4` |

---

### Release Notes

<details>
<summary>gomods/athens (gomods/athens)</summary>

###
[`v0.15.4`](https://redirect.github.com/gomods/athens/releases/tag/v0.15.4)

[Compare
Source](https://redirect.github.com/gomods/athens/compare/v0.15.3...v0.15.4)

#### What's Changed

- Support using redis urls to construct the redis client by
[@&#8203;opalmer](https://redirect.github.com/opalmer) in
[https://github.com/gomods/athens/pull/1994](https://redirect.github.com/gomods/athens/pull/1994)
- Fix typo preventing git-credential-github-app being installed by
[@&#8203;bradleyjkemp](https://redirect.github.com/bradleyjkemp) in
[https://github.com/gomods/athens/pull/1995](https://redirect.github.com/gomods/athens/pull/1995)
- update-go-pkg(deps): bump github.com/spf13/afero from 1.8.2 to 1.11.0
by [@&#8203;dependabot](https://redirect.github.com/dependabot) in
[https://github.com/gomods/athens/pull/1960](https://redirect.github.com/gomods/athens/pull/1960)

#### New Contributors

- [@&#8203;opalmer](https://redirect.github.com/opalmer) made their
first contribution in
[https://github.com/gomods/athens/pull/1994](https://redirect.github.com/gomods/athens/pull/1994)
- [@&#8203;bradleyjkemp](https://redirect.github.com/bradleyjkemp) made
their first contribution in
[https://github.com/gomods/athens/pull/1995](https://redirect.github.com/gomods/athens/pull/1995)

**Full Changelog**:
gomods/athens@v0.15.3...v0.15.4

</details>

---

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---

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charts/athens-proxy/Chart.yaml

@@ -1,7 +1,7 @@
 apiVersion: v1
 name: athens-proxy
-version: 0.14.2
-appVersion: v0.15.3
+version: 0.14.3
+appVersion: v0.15.4
 kubeVersion: ">= 1.19-0"
 description: The proxy server for Go modules
 icon: https://raw.githubusercontent.com/gomods/athens/main/docs/static/banner.png