Drop ValueSet forward declarations from headers not actually using the class. Forward-declare the class in cui/source/inc/numpages.hxx which actually uses it, but didn't forward-declare it or include the header yet, but previously got the forward-declaration from an included header. Change-Id: I8876ad47eb362f581aa41ee4a61a85c4093a1dd0 Reviewed-on: https://gerrit.libreoffice.org/c/core/+/211881 Reviewed-by: Michael Weghorn <m.weghorn@posteo.de> Tested-by: Jenkins