RFR(XS): 8170857: Typo in -Xlog:help output

[Marcus Larsson]

Hi,

Please review the following trivial fix of a typo in the -Xlog:help output.

Issue:
https://bugs.openjdk.java.net/browse/JDK-8170857

Webrev:
http://cr.openjdk.java.net/~mlarsson/8170857/webrev.00

Thanks,
Marcus