minor #5619 Remove a caution note about StringUtils::equals() which is no longer true (javiereguiluz)

This PR was merged into the 2.3 branch.

Discussion
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Remove a caution note about StringUtils::equals() which is no longer true

| Q             | A
| ------------- | ---
| Doc fix?      | yes
| New docs?     | no
| Applies to    | all
| Fixed tickets | #5618

Commits
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d0f1a4e Remove a cauion note about StringUtils::equals() which is no longer true

Author: wouterj

components/security/secure_tools.rst

@@ -21,11 +21,6 @@ algorithm; you can use the same strategy in your own code thanks to the
     // is some known string (e.g. password) equal to some user input?
     $bool = StringUtils::equals($knownString, $userInput);
 
-.. caution::
-
-    To avoid timing attacks, the known string must be the first argument
-    and the user-entered string the second.
-
 Generating a Secure random Number
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~