ministat.1: Match actual output

[jlduran]

Summary

Fix a documentation discrepancy, where the implementation was updated to
use uncertainty propagation for the ratio of means, but the example
output in the manual page was left unchanged.

Update the manual page example from 70.7384% to 102.3% to reflect the
actual output.

Fixes: a304ad90e9ae ("Reduce the bogosity of ministat's % difference calculations.")

[jlduran]

Fix the output in the README file as well.