Bump virtualenv in /requirements in the pip group across 1 directory

Bumps the pip group with 1 update in the /requirements directory: [virtualenv](https://github.com/pypa/virtualenv).


Updates `virtualenv` from 20.26.3 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@20.26.3...20.26.6)

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

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

Author: dependabot[bot]

requirements/requirements-ci.lock.txt

@@ -360,7 +360,7 @@ urllib3==2.2.2
     #   types-requests
 uvicorn==0.30.6
     # via sphinx-autobuild
-virtualenv==20.26.3
+virtualenv==20.26.6
     # via
     #   -r requirements/requirements-test.lock.txt
     #   tox

requirements/requirements-dev.lock.txt

@@ -502,7 +502,7 @@ uvicorn==0.30.6
     # via
     #   -r requirements/requirements-ci.lock.txt
     #   sphinx-autobuild
-virtualenv==20.26.3
+virtualenv==20.26.6
     # via
     #   -r requirements/requirements-ci.lock.txt
     #   tox

requirements/requirements-test.lock.txt

@@ -98,5 +98,5 @@ uritemplate==4.1.1
     # via coreapi
 urllib3==2.2.2
     # via requests
-virtualenv==20.26.3
+virtualenv==20.26.6
     # via tox