math.text.english: fix spelling of some numbers
math.text.english: fix spelling of some numbers

Replace some prefixes sex-, tre- and sept- with ses-, tres- and septem-
correspondingly.

It's also possible to replace "sexdecillion" with "sedecillion" and
"novemdecillion" with "novendecillion", but I decided to keep the old
words, since they are in the dictionaries.

See https://en.wikipedia.org/wiki/Names_of_large_numbers.

mrjbq7/factor,mrjbq7/factor,factor/factor,tgunr/factor,tgunr/factor,tgunr/factor,mrjbq7/factor,factor/factor,mrjbq7/factor,factor/factor,mrjbq7/factor,mrjbq7/factor,factor/factor,tgunr/factor,tgunr/factor,factor/factor,tgunr/factor,factor/factor