Bump pipenv from 2026.0.3 to 2026.5.1 (#2065)

* Bump pipenv from 2026.0.3 to 2026.5.1

Bumps [pipenv](https://github.com/pypa/pipenv) from 2026.0.3 to 2026.5.1.
- [Release notes](https://github.com/pypa/pipenv/releases)
- [Changelog](https://github.com/pypa/pipenv/blob/main/CHANGELOG.md)
- [Commits](pypa/pipenv@v2026.0.3...v2026.5.1)

---
updated-dependencies:
- dependency-name: pipenv
  dependency-version: 2026.5.1
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

* Add changelog entry

---------

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

Author: dependabot[bot]

CHANGELOG.md

@@ -2,6 +2,7 @@
 
 ## [Unreleased]
 
+- Updated Pipenv from 2026.0.3 to 2026.5.1. ([#2065](https://github.com/heroku/heroku-buildpack-python/pull/2065))
 - Updated Poetry from 2.3.2 to 2.3.3. ([#2064](https://github.com/heroku/heroku-buildpack-python/pull/2064))
 - Updated uv from 0.10.9 to 0.11.3. ([#2067](https://github.com/heroku/heroku-buildpack-python/pull/2067))
 

requirements/pipenv.txt

@@ -1 +1 @@
-pipenv==2026.0.3
+pipenv==2026.5.1