minor #20538 [HttpFoundation] Mention issues with generated URL hashes (javiereguiluz)

This PR was merged into the 6.4 branch.

Discussion
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[HttpFoundation] Mention issues with generated URL hashes

Related to #20481.

In #20508 we mention that "this problem no longer exist in 7.3". But, I think we should also mention that problem in all the branches before 7.3.

Commits
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357a3e9 [HttpFoundation] Mention issues with generated URL hashes

Author: javiereguiluz

routing.rst

@@ -2805,6 +2805,12 @@ service, which you can inject in your services or controllers::
     ``Symfony\Component\HttpKernel\UriSigner`` to
     ``Symfony\Component\HttpFoundation\UriSigner``.
 
+.. note::
+
+    The generated URI hashes may include the ``/`` and ``+`` characters, which
+    can cause issues with certain clients. If you encounter this problem, replace
+    them using the following: ``strtr($hash, ['/' => '_', '+' => '-'])``.
+
 Troubleshooting
 ---------------