This reverts commit 0e22ec73.

Reason for revert: Breaks layout tests:
https://ci.chromium.org/p/v8/builders/luci.v8.ci/V8-Blink%20Linux%2064/28814

Original change's description:
> [regexp] Escape newlines when setting [[OriginalSource]]
> 
> This escapes LineTerminator characters in a regexp pattern when
> creating the string that will be stored in the [[OriginalSource]] slot.
> 
> As an example, the source property for all following objects will equal
> "\n" (a '\' character followed by 'n'):
> 
>   /\n/
>   new RegExp("\n")
>   new RegExp("\\n")
> 
> Bug: v8:1982, chromium:855009
> Change-Id: I3b539497a0697e3d51ec969cae49308b0b312a19
> Reviewed-on: https://chromium-review.googlesource.com/c/1384316
> Commit-Queue: Jakob Gruber <jgruber@chromium.org>
> Reviewed-by: Yang Guo <yangguo@chromium.org>
> Reviewed-by: Mathias Bynens <mathias@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#58387}

TBR=yangguo@chromium.org,jgruber@chromium.org,mathias@chromium.org

Change-Id: I1db7e6a0c6cd1cd995fe9f499458108e88dc8cb9
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: v8:1982, chromium:855009
Reviewed-on: https://chromium-review.googlesource.com/c/1386493Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/master@{#58396}