Bump pip from 25.3 to 26.0.1 in /ci/builder

Bumps [pip](https://github.com/pypa/pip) from 25.3 to 26.0.1.
- [Changelog](https://github.com/pypa/pip/blob/main/NEWS.rst)
- [Commits](pypa/pip@25.3...26.0.1)

---
updated-dependencies:
- dependency-name: pip
  dependency-version: 26.0.1
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

ci/builder/requirements-core.txt

@@ -3,5 +3,5 @@
 # It is extremely unlikely that we'll ever need additional packages here. Do not
 # add to this list without consulting with @testing!
 
-pip==25.3
+pip==26.0.1
 setuptools==80.10.2