Ignore missing package.html in checkstyle

Change-Id: I74eeb1f58d8f3dffc92e8dcdb3dc6d32efd82735

checkstyle/vaadin-checkstyle.xml

@@ -51,9 +51,11 @@
 
     <!-- Checks that a package-info.java file exists for each package. -->
     <!-- See http://checkstyle.sf.net/config_javadoc.html#JavadocPackage -->
+<!--
     <module name="JavadocPackage">
         <property name="severity" value="info" />
     </module>
+-->
 
     <!-- Checks whether files end with a new line. -->
     <!-- See http://checkstyle.sf.net/config_misc.html#NewlineAtEndOfFile -->