[system] createTheme() shouldn't have "use client"

### Steps to reproduce 🕹

Link to live example:

Steps:

1. Create a project with Next.js
2. Add in the layout

```js
import { getInitColorSchemeScript } from '@mui/material/styles';

  return (
    <html lang="en">
      <head>
        {getInitColorSchemeScript()}
      </head>
```

### Current behavior 😯

<img width="585" alt="Screenshot 2023-09-16 at 22 00 32" src="https://github.com/mui/material-ui/assets/3165635/ba4d70e3-100c-4d04-bd60-afc8c9eda914">


### Expected behavior 🤔

It works

### Context 🔦

- mui/material-ui#34905
- https://github.com/mui/material-ui/pull/38967
- https://twitter.com/amanzrx4/status/1742985809316417913

### Your environment 🌎

<details>
  <summary><code>npx @mui/envinfo</code></summary>

```
  Don't forget to mention which browser you used.
  Output from `npx @mui/envinfo` goes here.
```
</details>


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[system] createTheme() shouldn't have "use client" #42750

Steps to reproduce 🕹

Current behavior 😯

Expected behavior 🤔

Context 🔦

Your environment 🌎

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