howto: Word parallel-programming-as-engineering less obscurely

The "where ... once ... becoming" wording might be legal English, it
is a bit obscure and less than friendly to those whose native language
is not English.  This commit therefore rewrites the offending paragraph.

Reported-by: Akira Yokosawa <akiyks@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
1 file changed