themed useCreateStyles leaks style tags in StrictMode

__Expected behavior:__
`` elements get disposed when re-rendering in StrictMode.

__Describe the bug:__
When using themed styles (possibly prop-based as well) re-rendering a component using `useStyles` with a new theme will leak their `<style>` elements.

This is possibly due to useStyles managing the sheet during render but unmanaging it in a effect cleanup. A component can render multiple times (in concurrent and strict mode) before an effect is scheduled.

__Codesandbox link:__
https://codesandbox.io/s/determined-wood-8d0s7?file=/src/App.js:513-622

Click "rerender" and see that the number of `<style>` element grows with every "rerender" click.

__Versions (please complete the following information):__
- react-jss: 10.1.1
- Browser [e.g. chrome, safari]: Chrome 81
- OS [e.g. Windows, macOS]: Ubuntu 18.04
- react: 16.13.1

Start with the linked CodeSandbox and reproduce the leak by clicking "rerender" while watching the number of elements. Trace useStyles and its theme-related sheet management across render and effect cleanup; done means repeated StrictMode rerenders no longer increase the style-element count.

Written by the indexing model from the issue text.