Invisible Unicode Character 'FORM FEED (FF)' (U+000C) is always injected into image-set CSS rule

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**Current behavior:**



After upgrading to React v18.2.0 and Emotion v11.10.5, Emotion components started to insert an invisible character inside CSS `image-set` and `-webkit-image-set` rules. It always appears in the first `url()` after first `&` character. 



Inserted character looks like some sort of invisible space and breaks CSS. Examples of broken CSS -



![image](https://user-images.githubusercontent.com/974035/202289205-6425a8db-12e6-440a-8142-15ad12310b50.png)



**To reproduce:**



Use this link - https://codesandbox.io/s/confident-water-tsbbj6?file=/src/App.js



1. Check WorkingExample in DevConsole and notice that `backround-image` CSS is correctly recognized by browser

![image](https://user-images.githubusercontent.com/974035/202288320-c81988da-0473-4734-b67c-238e3e94dc72.png)



2. Check BrokenExample in DevConsole and notice that `backround-image` CSS in invalid -



![image](https://user-images.githubusercontent.com/974035/202289795-4666388b-7d5b-4605-b66f-07246da25bc1.png)



You can copy-paste CSS from BrokenExample into some [CSS Validator](https://www.cssportal.com/css-validator/) to see this invisible char -



<img width="915" alt="image" src="https://user-images.githubusercontent.com/974035/202288939-23c75dc3-4bf6-4abd-9fc5-1051aa30a141.png">





**Expected behavior:**



`background-image` with `image-set` and `-webkit-image-set` rules work as expected.



**Environment information:**



<!-- Provide the `react` and `@emotion/*` packages versions -->



- `react` version: 18.2.0

- `@emotion/react` version: 11.10.5

- `@emotion/styled` version: 11.10.5

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