Fix config.ramps-v1.3.h.

Finally had to look it up myself. RAMPS users are apparently all
incapable or too stupid to write such fixes into an issue report.

From IRC:

xxx: oh, motors move now, thanks for helping
yyy: please write the changes into a github issue
xxx: will do
...
xxx: have to run now

... and these are the last words the world reads about xxx :-)
Observed three times now.