Revert "Blacklist test while failing."

This reverts commit 4f743c010604eda9fa8f4b5db19b5b295bc0885e.

The broken test has now been fixed. It has also been moved into a
separate class so this expection will not prevent any tests from
being run anyway.

Bug: 132100102
Test: atest \
    CtsLibcoreTestCases:libcore.java.lang.reflect.annotations.RetentionPolicyTest \
    CtsLibcoreTestCases:libcore.java.lang.reflect.annotations.AnnotationsTest

Change-Id: If68edcbee9b427cf2fd4810aa664bb83816154d3
diff --git a/tools/libcore_failures.txt b/tools/libcore_failures.txt
index 5b3d4c9..d65134c 100644
--- a/tools/libcore_failures.txt
+++ b/tools/libcore_failures.txt
@@ -242,13 +242,5 @@
   names: [
     "libcore.libcore.io.OsTest#testCrossFamilyBindConnectSendto"
   ]
-},
-{
-  description: "Unexpected failure",
-  result: EXEC_FAILED,
-  bug: 132100102,
-  names: [
-    "libcore.java.lang.reflect.annotations.AnnotationsTest#testRetentionPolicy_targetSdkVersion_23"
-  ]
 }
 ]