Fix 055-enum-performance.

Track change in OpenJdk exception message.

Change-Id: I91ab2421cc2d4a3961acb39361805bb9e13a447a
diff --git a/test/055-enum-performance/src/Main.java b/test/055-enum-performance/src/Main.java
index d5903af..d6bb211 100644
--- a/test/055-enum-performance/src/Main.java
+++ b/test/055-enum-performance/src/Main.java
@@ -20,7 +20,7 @@
             throw new AssertionError();
         } catch (InvocationTargetException expected) {
             IllegalArgumentException iae = (IllegalArgumentException) expected.getCause();
-            if (!iae.getMessage().equals("class java.lang.String is not an enum type")) {
+            if (!iae.getMessage().equals("class java.lang.String is not an enum type.")) {
                 throw new AssertionError();
             }
         }