ci: bump virtualenv from 20.26.3 to 20.26.4 in /.github/workflows (#152)

Author: dependabot[bot]

.github/workflows/constraints.txt

@@ -2,6 +2,6 @@ pip==24.2
 nox==2024.4.15
 nox-poetry==1.0.3
 poetry==1.8.3
-virtualenv==20.26.3
+virtualenv==20.26.4
 poetry-dynamic-versioning==1.4.0
 toml==0.10.2