minor #19575 Remove function getSalt() from security user class (rosier)

This PR was merged into the 6.4 branch.

Discussion
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Remove function getSalt() from security user class

The method getSalt() is no longer part of the UserInterface

Commits
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95fec6e Remove function getSalt() from security user class

Author: javiereguiluz

security.rst

@@ -193,17 +193,6 @@ from the `MakerBundle`_:
             return $this;
         }
 
-        /**
-         * Returning a salt is only needed if you are not using a modern
-         * hashing algorithm (e.g. bcrypt or sodium) in your security.yaml.
-         *
-         * @see UserInterface
-         */
-        public function getSalt(): ?string
-        {
-            return null;
-        }
-
         /**
          * @see UserInterface
          */