Remove Md5PasswordEncoder from core

Issue: gh-4674

core/src/main/java/org/springframework/security/authentication/encoding/Md5PasswordEncoder.java

@@ -1,42 +0,0 @@
-/*
- * Copyright 2004, 2005, 2006 Acegi Technology Pty Limited
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-package org.springframework.security.authentication.encoding;
-
-/**
- * <p>
- * MD5 implementation of PasswordEncoder.
- * </p>
- * <p>
- * If a <code>null</code> password is presented, it will be treated as an empty
- * <code>String</code> ("") password.
- * </p>
- * <P>
- * As MD5 is a one-way hash, the salt can contain any characters.
- * </p>
- *
- * This is a convenience class that extends the {@link MessageDigestPasswordEncoder} and
- * passes MD5 as the algorithm to use.
- *
- * @author Ray Krueger
- * @author colin sampaleanu
- * @author Ben Alex
- */
-public class Md5PasswordEncoder extends MessageDigestPasswordEncoder {
-
-	public Md5PasswordEncoder() {
-		super("MD5");
-	}
-}