spelling.txt: "modeled" is spelt correctly

No need to correct the correct.

Link: http://lkml.kernel.org/r/1472490791.3425.38.camel@perches.com


Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>