searchview: save a column in &x=t thread skeleton

searchview: save a column in &x=t thread skeleton

Displaying "100%" wastes a precious column.  Show "99%" instead
since there's little practical difference and <xapian/mset.h>
states:

  Note that these generally aren't percentages of anything meaningful
  (unless you use a custom weighting formula where they are!)

And we're not using a custom weighting formula.