chore(deps): update gitroomhq/postiz-app to v2.20.0 (#4469)

This PR contains the following updates:

| Package | Update | Change |
|---|---|---|
| ghcr.io/gitroomhq/postiz-app | minor | `v2.19.0` → `v2.20.0` |
| [gitroomhq/postiz-app](https://github.com/gitroomhq/postiz-app) | minor | `v2.19.0` → `v2.20.0` |

---

### Release Notes

<details>
<summary>gitroomhq/postiz-app (gitroomhq/postiz-app)</summary>

### [`v2.20.0`](https://github.com/gitroomhq/postiz-app/releases/tag/v2.20.0): MCP OAuth2, Organization Auth &amp; Platform Fixes

[Compare Source](https://github.com/gitroomhq/postiz-app/compare/v2.19.0...v2.20.0)

#### What's New

##### MCP OAuth2

- OAuth2 authentication support for MCP
- Separate MCP URL configuration
- Re-added SSE option for MCP

##### Organization Auth Flow

- Added organization to authentication flow
- Enhanced API capabilities

##### Improvements

- Agent media support
- Updated X (Twitter) API
- Facebook and Instagram connect improvements
- Google My Business pagination
- Redis throttler for rate limiting
- Temporal TLS and API key support
- Multiple SSE support
- Updated Stripe version
- Billing screen logout
- Show package info

##### Fixes

- Telegram posting fix
- Fixed extra space in sets
- Better TikTok error messages
- Collaborators fix in carousel posts
- Fixed TLS attribute registration
- Fixed email address for security vulnerability reporting
- Fixed delete error handling
- Subscription validation before posting
- Only process successful charges
- Refund and cancellation handling

**Full Changelog**: <https://github.com/gitroomhq/postiz-app/compare/v2.19.0...v2.20.0>

</details>

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---

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---

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Reviewed-on: #4469
Co-authored-by: Renovate Bot <renovate-bot@alexlebens.net>
Co-committed-by: Renovate Bot <renovate-bot@alexlebens.net>

clusters/cl01tl/helm/postiz/Chart.yaml

@@ -41,4 +41,4 @@ dependencies:
     repository: oci://harbor.alexlebens.net/helm-charts
 icon: https://cdn.jsdelivr.net/gh/selfhst/icons/png/postiz.png
 # renovate: datasource=github-releases depName=gitroomhq/postiz-app
-appVersion: v2.19.0
+appVersion: v2.20.0