mtd: nand: remove duplicate comment line

Commit 7854d3f7 ("mtd: spelling, capitalization, uniformity") added
a correctly spelled line, but failed to remove the wrongly spelled one.
Commit 064a7694 ("mtd: Fix typo mtd/tests") then fixed the spelling
again, but left the duplication.

Fixes: 7854d3f7 ("mtd: spelling, capitalization, uniformity")
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>