Method is overriden but not used anywhere in module so removing it.
Integrated into 'main-golden', will be available in build *200902180201* on http://bits.netbeans.org/dev/nightly/ (upload may still be in progress)
User: Marek Slama <email@example.com>
Log: #158608: Remove override of java.awt.Component.isValid()
Verified with NetBeans IDE Dev (Build 200902231401)