correct issue with session replay live mode and bundled css (highligh…

…t#9186)

## Summary

rrweb-io/rrweb#1458 introduced issues with
certain customers' applications such as:
```js
Uncaught CssSyntaxError: <css input>:1778:83: Unknown word
Uncaught CssSyntaxError: <css input>:1:65502: Unknown word
Uncaught CssSyntaxError: <css input>:1:2: Unclosed block
```

example of such a session:
https://app.highlight.io/92422/sessions/qGaSpGVNh4Ewqj8k23lNC5zNtcB1
affected highlight.run clients are >=9.1.5 with certain bundled CSS

this may also affect the replayer so the new frontend usage of rrweb is
affected

## How did you test this change?

fixes playback of [session that used to not
play](https://app.highlight.io/92422/sessions/qGaSpGVNh4Ewqj8k23lNC5zNtcB1)
<img width="1487" alt="Screenshot 2024-08-19 at 15 54 49"
src="https://github.com/user-attachments/assets/305779eb-6ee4-489f-999c-3c608f04d86b">

new client build working
<img width="1403" alt="Screenshot 2024-08-19 at 16 07 24"
src="https://github.com/user-attachments/assets/f6a46f8f-827f-42b0-acc2-cd01fc2ae249">

## Are there any deployment considerations?

new changeset

## Does this work require review from our design team?

no

.changeset/chilled-ads-change.md

@@ -0,0 +1,7 @@
+---
+'highlight.run': patch
+---
+
+revert postcss changes to css parsing in rrweb
+https://github.com/rrweb-io/rrweb/pull/1458 introduced
+a new CSS parser which causes issues with certain large CSS files