SEC-1304: Removed compareTo method from GrantedAuthorityImpl

This method had been left by mistake when the Comparable 
interface was removed. See also SEC-1347.

core/src/test/java/org/springframework/security/core/authority/GrantedAuthorityImplTests.java

@@ -61,30 +61,12 @@ public class GrantedAuthorityImplTests {
         assertEquals("TEST", auth.toString());
     }
 
-    @Test
-    public void compareToGrantedAuthorityWithSameValueReturns0() {
-        assertEquals(0, new GrantedAuthorityImpl("TEST").compareTo(new MockGrantedAuthority("TEST")));
-    }
-
-    @Test
-    public void compareToNullReturnsNegativeOne() {
-        assertEquals(-1, new GrantedAuthorityImpl("TEST").compareTo(null));
-    }
-
-    /* SEC-899 */
-    @Test
-    public void compareToHandlesCustomAuthorityWhichReturnsNullFromGetAuthority() {
-        assertEquals(-1, new GrantedAuthorityImpl("TEST").compareTo(new MockGrantedAuthority()));
-    }
 
     //~ Inner Classes ==================================================================================================
 
     private class MockGrantedAuthority implements GrantedAuthority {
         private String role;
 
-        public MockGrantedAuthority() {
-        }
-
         public MockGrantedAuthority(String role) {
             this.role = role;
         }