blacklist ocSheet for threaded calc

It asserts in thread-unsafe ScDocument::GetTable().

Change-Id: I82ce5a0c977cda01fe4d372571e3f8826459dc33
Reviewed-on: https://gerrit.libreoffice.org/63179
Tested-by: Jenkins
Reviewed-by: Luboš Luňák <l.lunak@collabora.com>

sc/source/core/tool/token.cxx

@@ -1299,6 +1299,7 @@ void ScTokenArray::CheckForThreading( const FormulaToken& r )
         ocDBVar,
         ocDBVarP,
         ocText,
+        ocSheet,
         ocExternal,
         ocDde,
         ocWebservice,