minor #11139 Update security_checker.rst (shreypuranik)

This PR was squashed before being merged into the 3.4 branch (closes #11139).

Discussion
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Update security_checker.rst

Adding a small note advising users to always use the latest version of the command, as old versions will now break existing build plans because change of composer.lock checking tool.

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Commits
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668b4f8 Update security_checker.rst

Author: javiereguiluz

security/security_checker.rst

@@ -25,6 +25,14 @@ FriendsOfPHP organization.
     This way you can add it to your project build process and your continuous
     integration workflows to make them fail when there are vulnerabilities.
 
+.. tip::
+
+    Earlier versions of this command used a tool hosted at a now deprecated URL,
+    with the tool having since been moved to a new location, which has been 
+    reflected in newer versions of the bundle. Use the latest version of the 
+    command to avoid getting exit code zero and breaking existing build plans
+    if the command has been integrated into project build process.
+    
 .. note::
 
     To enable the ``security:check`` command, make sure the