Remove unneeded assertion disjunction in engine

This commit removes an unneeded disjunction in an assertion in the
engine.

Author: jasontedor

core/src/main/java/org/elasticsearch/index/engine/Engine.java

@@ -361,7 +361,7 @@ public Operation.TYPE getOperationType() {
 
         void setTranslogLocation(Translog.Location translogLocation) {
             if (freeze.get() == null) {
-                assert failure == null || translogLocation == null: "failure has to be null to set translog location";
+                assert failure == null : "failure has to be null to set translog location";
                 this.translogLocation = translogLocation;
             } else {
                 throw new IllegalStateException("result is already frozen");