[6.x] preg_replace_array remove needless foreach

[dmitryuk]

Remove needless foreach from preg_replace_array helper.

[GrahamCampbell]

Sorry but this isn't correct. The foreach is doing the job of handling the two different cases:

1. The array is empty.
2. The array is of size at least 1.

Your code doesn't handle the empty case properly.

[SjorsO]

@dmitryuk I was writing some tests for the preg_replace_array, and turns out you were right, the foreach is unnecessary. I've opened a new PR #31504