Bump pip from 25.3 to 26.0 in /pysplashsurf/pysplashsurf/docs

Bumps [pip](https://github.com/pypa/pip) from 25.3 to 26.0.
- [Changelog](https://github.com/pypa/pip/blob/main/NEWS.rst)
- [Commits](pypa/pip@25.3...26.0)

---
updated-dependencies:
- dependency-name: pip
  dependency-version: '26.0'
  dependency-type: direct:production
...

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

Author: dependabot[bot]

pysplashsurf/pysplashsurf/docs/requirements.txt

@@ -1,4 +1,4 @@
-pip==25.3
+pip==26.0
 sphinx==8.2.3
 numpy==2.2.3
 meshio==5.3.5