PHP: fix ambiguous wording in eval() paragraph (#158)

* PHP: fix ambiguous wording in eval() paragraph

The original sentence "Both of these must not be used" was changed
to "Neither of these must be used" in 4361cec (PR 65), based on
a suggestion noting the original sentence read weird.

However, it seems to me that "Neither of these must be used" can
be read as "there is no requirement to use either" instead of the
intended prohibition.

This commit fixes this ambiguity.

---------

Co-authored-by: Gary Jones <github@garyjones.io>

Author: rodrigoprimo

wordpress-coding-standards/php.md

@@ -991,7 +991,9 @@ switch ( $foo ) {
 
 The `goto` statement must never be used.
 
-The `eval()` construct is _very dangerous_ and is impossible to secure. Additionally, the `create_function()` function, which internally performs an `eval()`, is deprecated since PHP 7.2 and has been removed in PHP 8.0. Neither of these must be used.
+The `eval()` construct is _very dangerous_ and is impossible to secure. It must not be used.
+
+The `create_function()` function internally performs an `eval()`. It was deprecated in PHP 7.2 and removed in PHP 8.0. It must not be used.
 
 ### Closures (Anonymous Functions)