Remove java/lang/management/ThreadMXBean/ThreadStateTest.java from ProblemList.txt

java/lang/management/ThreadMXBean/ThreadStateTest.java has been fixed in [1]. jdk/test/ProblemList.txt should also be updated.

$ hg diff ProblemList.txt
diff --git a/test/ProblemList.txt b/test/ProblemList.txt
--- a/test/ProblemList.txt
+++ b/test/ProblemList.txt
@@ -122,9 +122,6 @@

 # jdk_lang

-# 6944188
-java/lang/management/ThreadMXBean/ThreadStateTest.java generic-all
-
 # 7067973
 java/lang/management/MemoryMXBean/CollectionUsageThreshold.java generic-all