pull request #798 - fix typo in disclosure \

of vanquired monsters.

Pull request from janne-hmp:  the test for how many spaces to insert
in front of "the <unique monster>" couldn't match prefix "the "
because it was specifying a length of 3 instead of the 4 required to
include the trailing space.

Despite that clear error, the code worked as intended because the
default value of 0 is the same as an explicit value of 0 it would
have gotten if it had matched "the ".  So there is no change in the
resulting vanquished monsters display.

Closes #798