Fix bug 668530

* In budget flow report options, change the maximum value
  for period to 60 (Note the FIXMEs)

Author: Robert Ratliff <ratliff.bobby@gmail.com>

git-svn-id: svn+ssh://svn.gnucash.org/repo/gnucash/trunk@23300 57a11ea4-9604-0410-9ed3-97b8803252fd