Bump pip from 26.0.1 to 26.1.1 (#563)

Bumps [pip](https://github.com/pypa/pip) from 26.0.1 to 26.1.1.
- [Changelog](https://github.com/pypa/pip/blob/main/NEWS.rst)
- [Commits](pypa/pip@26.0.1...26.1.1)

---
updated-dependencies:
- dependency-name: pip
  dependency-version: 26.1.1
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

CHANGELOG.md

@@ -9,6 +9,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Changed
 
+- Updated pip from 26.0.1 to 26.1.1. ([#563](https://github.com/heroku/buildpacks-python/pull/563))
 - Updated uv from 0.11.6 to 0.11.11. ([#562](https://github.com/heroku/buildpacks-python/pull/562))
 
 ## [6.4.1] - 2026-04-13

requirements/pip.txt

@@ -1 +1 @@
-pip==26.0.1
+pip==26.1.1