Bump epix from 0.3.3 to 0.3.4 in /extra_requirements (#408)

Bumps [epix](https://github.com/XENONnT/epix) from 0.3.3 to 0.3.4.
- [Release notes](https://github.com/XENONnT/epix/releases)
- [Changelog](https://github.com/XENONnT/epix/blob/master/HISTORY.md)
- [Commits](XENONnT/epix@v0.3.3...v0.3.4)

---
updated-dependencies:
- dependency-name: epix
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

extra_requirements/requirements-tests.txt

@@ -1,4 +1,4 @@
 strax==1.4.1
 straxen==2.0.5
-epix==0.3.3
+epix==0.3.4
 git+https://github.com/XENONnT/ax_env