manuals: remove repeated word

The word "modern" appears twice, remove the extra one.

(From yocto-docs rev: 8a2169431551ea29bf45b2eb120a13f0e444e1ea)

Signed-off-by: Andrew Kreimer <algonell@gmail.com>
Signed-off-by: Antonin Godard <antonin.godard@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

documentation/brief-yoctoprojectqs/index.rst

@@ -44,7 +44,7 @@ following requirements:
    much more will help to run multiple builds and increase
    performance by reusing build artifacts.
 
--  At least &MIN_RAM; Gbytes of RAM, though a modern modern build host with as
+-  At least &MIN_RAM; Gbytes of RAM, though a modern build host with as
    much RAM and as many CPU cores as possible is strongly recommended to
    maximize build performance.