Docs: Remove an obsolete function description in addslashes_gpc().

- Usage of `get_magic_quotes_gpc()` was removed from `addslashes_gpc()` in [46105] / #47783.
- A similar description fragment was removed from `wp_parse_str()` in that changeset, but this one was missed.
- The `get_magic_quotes_gpc()` function itself was deprecated in PHP 7.4 and removed in PHP 8.0.

Props mitweka, audrasjb, SergeyBiryukov.
Fixes #56233.
See #55646.


git-svn-id: https://develop.svn.wordpress.org/trunk@53776 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/formatting.php

@@ -2785,9 +2785,6 @@ function untrailingslashit( $string ) {
 /**
  * Adds slashes to a string or recursively adds slashes to strings within an array.
  *
- * Slashes will first be removed if magic_quotes_gpc is set, see {@link
- * https://www.php.net/magic_quotes} for more details.
- *
  * @since 0.71
  *
  * @param string|array $gpc String or array of data to slash.