Bump virtualenv from 20.25.1 to 20.26.6 in /requirements (#35)

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Author: dependabot[bot]

requirements/dev.txt

@@ -22,7 +22,7 @@ pyyaml==6.0.1
     # via pre-commit
 ruff==0.3.4
     # via -r dev.in
-virtualenv==20.25.1
+virtualenv==20.26.6
     # via pre-commit
 
 # The following packages are considered to be unsafe in a requirements file: