Fix a Formatter test that I checked in broken.

There's really no excuse for this with DalvikRunner, but I copy and pasted this
from a mail, and didn't run it until after it had been committed. I mean, who
puts untested code in a mail? ;-)
diff --git a/libcore/luni/src/test/java/java/util/FormatterTest.java b/libcore/luni/src/test/java/java/util/FormatterTest.java
index 2adbbb4..11d82fb 100644
--- a/libcore/luni/src/test/java/java/util/FormatterTest.java
+++ b/libcore/luni/src/test/java/java/util/FormatterTest.java
@@ -31,7 +31,7 @@
     // Creating a NumberFormat is expensive, so we like to reuse them, but we need to be careful
     // because they're mutable.
     public void test_NumberFormat_reuse() throws Exception {
-        assertEquals("7.000000 7", String.format("%.6f %d", 7, 7));
+        assertEquals("7.000000 7", String.format("%.6f %d", 7.0, 7));
     }
 
     public void test_formatNull() throws Exception {