doc/features: remove duplicate word in distribution feature ext2

(From yocto-docs rev: fa846606014a85154b63794a17ff1d9aacc1a7bc)

Signed-off-by: Jörg Sommer <joerg.sommer@navimatix.de>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Steve Sakoman <steve@sakoman.com>