Migrate from deprecated getDisplaySubject() to equivalent actualAsStr…

…ing().

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=185692362

core/src/main/java/com/google/common/truth/PrimitiveByteArraySubject.java

@@ -57,7 +57,7 @@ public void isEqualTo(Object expected) {
       if (!Arrays.equals(actual, expectedArray)) {
         failComparing(
             "Not true that "
-                + getDisplaySubject()
+                + actualAsString()
                 + " is equal to <"
                 + Arrays.toString(expectedArray)
                 + ">;",