Revert "ART: Blacklist a libcore test for investigation"

This reverts commit fc3bb5c83d92d45011bef71ac62621f9707ee179.

The test is now fixed.

Bug: 28826195
Change-Id: I2fb9bb5250f834f8535ec392a209cbc84de8781c
diff --git a/tools/libcore_failures.txt b/tools/libcore_failures.txt
index bdcf86d..f25fb98 100644
--- a/tools/libcore_failures.txt
+++ b/tools/libcore_failures.txt
@@ -248,11 +248,6 @@
   names: [ "libcore.java.io.FileTest#testJavaIoTmpdirMutable" ]
 },
 {
-  description: "Investigate whether the test is making a wrong assumption with the newly enforced classpath.",
-  result: EXEC_FAILED,
-  names: ["dalvik.system.DexClassLoaderTest#testDexThenPathClassLoader"]
-},
-{
   description: "Made for extending, shouldn't be run",
   result: EXEC_FAILED,
   names: ["jsr166.CollectionTest#testEmptyMeansEmpty",