[Rd] model.tabels warning refers to wrong function (PR#6839)

[cmoffet at nwrc.ars.usda.gov]

Full_Name: Corey A. Moffet
Version: 1.8.1
OS: Windows 2000 and RHL 9
Submission from: (NULL) (199.133.140.156)


The function model.tables.aov and perhaps other model.tables methods refer the
user to use the function se.contrasts when the design is unbalanced.  The
function name is se.contrast (singular).