build(deps): update c2cwsgiutils[broadcast] requirement

Updates the requirements on [c2cwsgiutils[broadcast]](https://github.com/camptocamp/c2cwsgiutils) to permit the latest version.
- [Release notes](https://github.com/camptocamp/c2cwsgiutils/releases)
- [Changelog](https://github.com/camptocamp/c2cwsgiutils/blob/master/BREAKING_CHANGES.md)
- [Commits](camptocamp/c2cwsgiutils@4.0.0...6.0.8)

---
updated-dependencies:
- dependency-name: c2cwsgiutils[broadcast]
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>

requirements.txt

@@ -1,5 +1,5 @@
 boto3==1.28.42
-c2cwsgiutils[broadcast]>=4.0,<5
+c2cwsgiutils[broadcast]>=4.0,<7
 Pillow==10.2.0
 wand==0.6.11
 WebTest==3.0.0