Typo in PerformanceTuning.gdoc

[robertoschwald]

It states:

CATALINA_OPTS="-server -noverify -Xshare:off -Xms512M -Xmx512M -XX:MaxPermSize=256M -XX:PermSize=128M -XX:+UseParallelGC"

which has a typo. It must read "-Xshare:none", otherwise the VM doesn't start (at least Oracle JDK7 VM)