The same check will be done later in the job, so we can avoid to check
that in the UI in computeContainerAdornmentFlags() to avoid random UI
freezes.

Change-Id: I3e894a953081e80293f61493eed6427fd6c6fa4a
Signed-off-by: Andrey Loskutov <loskutov@gmx.de>
Reviewed-on: https://git.eclipse.org/r/c/jdt/eclipse.jdt.ui/+/190496
Tested-by: JDT Bot <jdt-bot@eclipse.org>