Bump ibek in the dev-dependencies group across 1 directory

Bumps the dev-dependencies group with 1 update in the / directory: [ibek](https://github.com/epics-containers/ibek).


Updates `ibek` from 1.7.2b6 to 3.0.0b6
- [Release notes](https://github.com/epics-containers/ibek/releases)
- [Changelog](https://github.com/epics-containers/ibek/blob/main/CHANGELOG.rst)
- [Commits](epics-containers/ibek@1.7.2b6...3.0.0b6)

---
updated-dependencies:
- dependency-name: ibek
  dependency-type: direct:production
  update-type: version-update:semver-major
  dependency-group: dev-dependencies
...

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

requirements.txt

@@ -1,3 +1,3 @@
 # these requirements are for additional python packages to install into the
 # container
-ibek==1.7.2b6
+ibek==3.0.0b6