typo in fix relax/box doc page

of the reference dimensions. If this is not the case, then the

converged stress tensor will not equal that specified by the user.  We

can resolve this problem by periodically resetting the reference

dimensions. The keyword {nreset_ref} controls how often this is done.

If this keyword is not used, or is given a value of zero, then the

dimensions. The keyword {nreset} controls how often this is done.  If

this keyword is not used, or is given a value of zero, then the

reference dimensions are set to those of the initial simulation domain

and are never changed. A value of {nstep} means that every {nstep}

minimization steps, the reference dimensions are set to those of the