ci: Prepare release 3.0.6

[fsbraun]

Description

Bumps version and updates change log

Related resources

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Checklist

• [ ] I have opened this pull request against master
• [ ] I have added or modified the tests when changing logic
• [ ] I have followed the conventional commits guidelines to add meaningful information into the changelog
• [ ] I have read the contribution guidelines and I have joined #workgroup-pr-review on Slack to find a “pr review buddy” who is going to review my pull request.

[codecov[bot]]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (68f6aaa) 75.22% compared to head (e668c1e) 75.22%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #1419 +/- ## ======================================= Coverage 75.22% 75.22% ======================================= Files 75 75 Lines 3455 3455 Branches 555 555 ======================================= Hits 2599 2599 Misses 691 691 Partials 165 165 ``` | [Files Changed](https://app.codecov.io/gh/django-cms/django-filer/pull/1419?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=django-cms) | Coverage Δ | | |---|---|---| | [filer/\_\_init\_\_.py](https://app.codecov.io/gh/django-cms/django-filer/pull/1419?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=django-cms#diff-ZmlsZXIvX19pbml0X18ucHk=) | `100.00% <100.00%> (ø)` | |

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