Bump virtualenv to 20.26.6

[radoering]

Pull Request Check List

Resolves: #issue-number-here

• Added tests for changed code.
• Updated documentation for changed code.

[poetry-bot]

The backport to 1.8 failed:

The process '/usr/bin/git' failed with exit code 1

To backport manually, run these commands in your terminal:

# Fetch latest updates from GitHub
git fetch
# Create a new working tree
git worktree add .worktrees/backport-1.8 1.8
# Navigate to the new working tree
cd .worktrees/backport-1.8
# Create a new branch
git switch --create backport-9757-to-1.8
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 863acd1f6fa6e9d103d9eb74a023394f75c15af4
# Push it to GitHub
git push --set-upstream origin backport-9757-to-1.8
# Go back to the original working tree
cd ../..
# Delete the working tree
git worktree remove .worktrees/backport-1.8

Then, create a pull request where the base branch is 1.8 and the compare/head branch is backport-9757-to-1.8.

[github-actions]

This pull request has been automatically locked since there has not been any recent activity after it was closed. Please open a new issue for related bugs.