0.85.1 of @nivo/bar breaks tooltips that use position: fixed style

[kariwhitcomb]

Describe/explain the bug
A clear and concise description of what the bug is.

When we upgraded to @nivo/bar 0.85.1 the custom tooltips we use on our bar charts stopped appearing

To Reproduce
https://codesandbox.io/p/sandbox/pedantic-keldysh-tfvysn

Steps to reproduce the behavior:

1. Hover over a bar in the chart
2. In the top one, it does not show the tooltip. The bottom one does. The only difference is that one has the style set.
3. If you change package.json to use 0.85.0 version, then both charts show the tooltip

Expected behavior

Both charts should show the tooltip.

Screenshots
If applicable, add screenshots to help explain your problem.

Desktop (please complete the following information):

• OS: MacOS
• Browser Chrome
• Version 123.0.6312.87

Additional context
Add any other context about the problem here.
The only change I can figure might have changed this behavior in 0.85.1 is https://github.com/plouc/nivo/pull/2480/files, but I don't understand why

[liringlas]

So basically position: fixed works for tooltips which CSS styles are applied by CSS className, not style attribute?
Maybe your style overrides the one which should be applied by nivo?

[plouc]

Seems related to #2480, the tooltip is there, but its opacity remains 0.