Bump attrs from 25.4.0 to 26.1.0 in /requirements/CI

Bumps [attrs](https://github.com/sponsors/hynek) from 25.4.0 to 26.1.0.
- [Commits](https://github.com/sponsors/hynek/commits)

---
updated-dependencies:
- dependency-name: attrs
  dependency-version: 26.1.0
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

requirements/CI/requirements.txt

@@ -9,7 +9,7 @@ sphinx-argparse==0.5.2
 sphinx-issues==5.0.1
 sphinx_rtd_theme==3.1.0
 sphinxcontrib-programoutput==0.18
-attrs==25.4.0
+attrs==26.1.0
 appdirs==1.4.4
 humanize==4.15.0
 pyslim==1.1.0