minor #20550 [Validator] Add note to version option in Cidr constraint (Ninos)

This PR was squashed before being merged into the 7.1 branch.

Discussion
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[Validator] Add note to `version` option in `Cidr` constraint

Added for some may relevant note...

Ref: #19503 #19117

Commits
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bb76fd9 [Validator] Add note to `version` option in `Cidr` constraint

Author: javiereguiluz

reference/constraints/Cidr.rst

@@ -126,6 +126,12 @@ Parameter        Description
 This determines exactly *how* the CIDR notation is validated and can take one
 of :ref:`IP version ranges <reference-constraint-ip-version>`.
 
+.. note::
+
+    IP range (``*_private``, ``*_reserved``) is only validating against IP, but not the whole
+    netmask. You need to set the ``{{ min }}`` value for the netmask to harden the validation a bit.
+    For example, ``9.0.0.0/6`` results to be ``*_public``, but also uses ``10.0.0.0/8`` range (``*_private``).
+
 .. versionadded:: 7.1
 
     The support of all IP version ranges was introduced in Symfony 7.1.