chore: Bump virtualenv in /sdk/python/requirements

Bumps [virtualenv](https://github.com/pypa/virtualenv) from 20.23.0 to 20.26.6.
- [Release notes](https://github.com/pypa/virtualenv/releases)
- [Changelog](https://github.com/pypa/virtualenv/blob/main/docs/changelog.rst)
- [Commits](pypa/virtualenv@20.23.0...20.26.6)

---
updated-dependencies:
- dependency-name: virtualenv
  dependency-type: direct:production
...

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

sdk/python/requirements/py3.10-ci-requirements.txt

@@ -1062,7 +1062,7 @@ uvicorn-worker==0.2.0
     # via feast (setup.py)
 uvloop==0.21.0
     # via uvicorn
-virtualenv==20.23.0
+virtualenv==20.26.6
     # via
     #   feast (setup.py)
     #   pre-commit

sdk/python/requirements/py3.11-ci-requirements.txt

@@ -1039,7 +1039,7 @@ uvicorn-worker==0.2.0
     # via feast (setup.py)
 uvloop==0.21.0
     # via uvicorn
-virtualenv==20.23.0
+virtualenv==20.26.6
     # via
     #   feast (setup.py)
     #   pre-commit

sdk/python/requirements/py3.9-ci-requirements.txt

@@ -1074,7 +1074,7 @@ uvicorn-worker==0.2.0
     # via feast (setup.py)
 uvloop==0.21.0
     # via uvicorn
-virtualenv==20.23.0
+virtualenv==20.26.6
     # via
     #   feast (setup.py)
     #   pre-commit