Removed unused constant in Mismatch test

Author: alexander-yevsyukov

client/src/test/java/org/spine3/base/MismatchShould.java

@@ -41,7 +41,6 @@
  */
 public class MismatchShould {
 
-    private static final String REQUESTED = "requested";
     private static final String EXPECTED = "expected";
     private static final String ACTUAL = "ACTUAL";
     private static final int VERSION = 0;