Remove generated Import-Package from vaadin-client MANIFEST.MF

Change-Id: If2f8a95917f92501920d8aaa332899b0cb36d996

client/pom.xml

@@ -174,6 +174,7 @@
 					<instructions>
 						<Bundle-RequiredExecutionEnvironment>JavaSE-1.6</Bundle-RequiredExecutionEnvironment>
 						<Export-Package>com.vaadin.*;version="${project.version}",com.google.*;version="${project.version}"</Export-Package>
+						<Import-Package></Import-Package>
 					</instructions>
 				</configuration>
 				<executions>