docs: ras: don't need to repeat twice the same thing

We don't need to say twice "for the first time" at the same
paragraph.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Link: https://lore.kernel.org/r/f76dcae96de8b1bb8ee37a79781c111c825e26d6.1586881715.git.mchehab+huawei@kernel.org


Signed-off-by: Jonathan Corbet <corbet@lwn.net>