Bump virtualenv from 20.26.2 to 20.28.0 in /tools/deps

Bumps [virtualenv](https://github.com/pypa/virtualenv) from 20.26.2 to 20.28.0.
- [Release notes](https://github.com/pypa/virtualenv/releases)
- [Changelog](https://github.com/pypa/virtualenv/blob/main/docs/changelog.rst)
- [Commits](pypa/virtualenv@20.26.2...20.28.0)

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

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

tools/deps/requirements-tox.txt

@@ -72,9 +72,9 @@ typing-extensions==4.12.2 \
     --hash=sha256:04e5ca0351e0f3f85c6853954072df659d0d13fac324d0072316b67d7794700d \
     --hash=sha256:1a7ead55c7e559dd4dee8856e3a88b41225abfe1ce8df57b7c13915fe121ffb8
     # via importlib-metadata
-virtualenv==20.26.2 \
-    --hash=sha256:82bf0f4eebbb78d36ddaee0283d43fe5736b53880b8a8cdcd37390a07ac3741c \
-    --hash=sha256:a624db5e94f01ad993d476b9ee5346fdf7b9de43ccaee0e0197012dc838a0e9b
+virtualenv==20.28.0 \
+    --hash=sha256:23eae1b4516ecd610481eda647f3a7c09aea295055337331bb4e6892ecce47b0 \
+    --hash=sha256:2c9c3262bb8e7b87ea801d715fae4495e6032450c71d2309be9550e7364049aa
     # via tox
 zipp==3.20.0 \
     --hash=sha256:0145e43d89664cfe1a2e533adc75adafed82fe2da404b4bbb6b026c0157bdb31 \