Fix vaadin-server/bnd.bnd file so it is compatible with Liferay 7.0 and (#11360)

7.1. (#11156)
* This the range might be necessary to increase when Liferay 7.2 or
newer has been released.

server/bnd.bnd

@@ -4,7 +4,7 @@ Bundle-Version: ${osgi.bundle.version}
 Bundle-RequiredExecutionEnvironment: JavaSE-1.8
 Bundle-License: http://www.apache.org/licenses/LICENSE-2.0
 Import-Package: com.vaadin.sass.*;resolution:=optional,\
-  com.liferay.portal.kernel.util;resolution:=optional,\
+  com.liferay.portal.kernel.util;resolution:=optional;version='[7.0.0,9.0.0)',\
   javax.portlet*;resolution:=optional,\
   javax.validation*;resolution:=optional;version='${javax.validation.version}',\
   org.atmosphere*;resolution:=optional;version='${atmosphere.runtime.version}',\