fix: blur toolbar event handler matches js lib approach

[pauldambra]

for https://posthoghelp.zendesk.com/agent/tickets/20804

in that ticket, and only in local dev, when they interact with the toolbar its menus close

there's no way to investigate this, since it's in local dev, so we have to probe instead. this makes the "is in toolbar" detection more like that used by the heatmap for no other reason than it's something to try 🙈

[github-actions[bot]]

Size Change: +71 B (+0.01%)

Total Size: 1.16 MB

ℹ️ View Unchanged

| Filename | Size | Change | | :--- | :---: | :---: | | `frontend/dist/toolbar.js` | 1.16 MB | +71 B (+0.01%) |

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