[9] RFR 8160611: Clean up ProblemList.txt for closed/resolved issues

[John Jiang]

Hi,
The below issues have been closed,
    JDK-8130339, JDK-8068645, JDK-8061177, JDK-8058616, JDK-8046285, 
JDK-8031555
but the associated items still be contained by ProblemList.txt. This 
small patch removes them.

Issue: https://bugs.openjdk.java.net/browse/JDK-8160611
Webrev: http://cr.openjdk.java.net/~jjiang/8160611/webrev.00

Best regards,
John Jiang