Bump query-monitor floor to ^3.20.4

[mikelittle]

Summary

• Raises the johnbillion/query-monitor constraint floor from ^3.20.2 to ^3.20.4 so fresh installs pick up the latest 3.20.x patch releases by default.
• v23–v26 remain on the 3.x line (master is already on ^4.0.6).

Test plan

• CI passes
• composer update johnbillion/query-monitor resolves to 3.20.4

🤖 Generated with Claude Code

[github-actions]

Successfully created backport PR for v23-branch:

• [Backport v23-branch] Bump query-monitor floor to ^3.20.4 #1062

[github-actions]

Successfully created backport PR for v24-branch:

• [Backport v24-branch] Bump query-monitor floor to ^3.20.4 #1063

[github-actions]

Successfully created backport PR for v25-branch:

• [Backport v25-branch] Bump query-monitor floor to ^3.20.4 #1064

[github-actions]

Backport failed for v26-branch, because it was unable to cherry-pick the commit(s).

Please cherry-pick the changes locally and resolve any conflicts.

git fetch origin v26-branch
git worktree add -d .worktree/backport-1058-to-v26-branch origin/v26-branch
cd .worktree/backport-1058-to-v26-branch
git switch --create backport-1058-to-v26-branch
git cherry-pick -x 0948db74556fe619e6ab098220cdffb7c13e6948

[github-actions]

After resolving conflicts, continue with:

# Add the resolved files
git add .
# Continue the cherry-pick
git cherry-pick --continue
# Push the branch to GitHub
git push --set-upstream origin backport-1058-to-v26-branch
# Go back to the original working tree
cd ../..
# Delete the working tree
git worktree remove .worktree/backport-1058-to-v26-branch

Then create a pull request using the GitHub CLI:

gh pr create --base v26-branch --head backport-1058-to-v26-branch --title "[Backport v26-branch] Bump query-monitor floor to ^3.20.4" --body "Backport of #1058 to \`v26-branch\`."