Build(deps): Bump virtualenv from 16.0.0 to 20.36.1 in /backend

Bumps [virtualenv](https://github.com/pypa/virtualenv) from 16.0.0 to 20.36.1.
- [Release notes](https://github.com/pypa/virtualenv/releases)
- [Changelog](https://github.com/pypa/virtualenv/blob/main/docs/changelog.rst)
- [Commits](pypa/virtualenv@16.0.0...20.36.1)

---
updated-dependencies:
- dependency-name: virtualenv
  dependency-version: 20.36.1
  dependency-type: direct:production
...

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

Author: dependabot[bot]

backend/requirements.txt

@@ -47,7 +47,7 @@ sqlparse==0.5.0
 typed-ast
 urllib3==1.25.11
 vine==1.3.0
-virtualenv==16.0.0
+virtualenv==20.36.1
 wrapt==1.11.2
 xlrd==1.2.0
 xlwt==1.3.0