Bump scipp from 25.5.0 to 25.5.1 in /requirements

Bumps [scipp](https://github.com/scipp/scipp) from 25.5.0 to 25.5.1.
- [Release notes](https://github.com/scipp/scipp/releases)
- [Commits](scipp/scipp@25.05.0...25.05.1)

---
updated-dependencies:
- dependency-name: scipp
  dependency-version: 25.5.1
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

Author: dependabot[bot]

requirements/base.txt

@@ -141,7 +141,7 @@ sciline==25.4.1
     # via
     #   -r base.in
     #   essreduce
-scipp==25.5.0
+scipp==25.5.1
     # via
     #   -r base.in
     #   essreduce