Disabled unit tests for multi-sheet references, see bug #55906

git-svn-id: https://svn.apache.org/repos/asf/poi/trunk@1613282 13f79535-47bb-0310-9956-ffa450edef68
#55906 Extern Sheet References can have a last as well as a first sheet

git-svn-id: https://svn.apache.org/repos/asf/poi/trunk@1613302 13f79535-47bb-0310-9956-ffa450edef68