docs/manual/beyond-buildroot: additional minor fixes

Those issues were noticed by Thomas De Schampheleire during the
review, but they were forgotten when applying the patch.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

docs/manual/beyond-buildroot.txt

@@ -38,13 +38,13 @@ You can test your live CD image using QEMU:
 qemu-system-i386 -cdrom output/images/rootfs.iso9660
 -------------------
 
-Or use it as a hard-drive image if it is an hybrid ISO:
+Or use it as a hard-drive image if it is a hybrid ISO:
 
 -------------------
 qemu-system-i386 -hda output/images/rootfs.iso9660
 -------------------
 
-It can be easily flashed to an USB drive with +dd+:
+It can be easily flashed to a USB drive with +dd+:
 
 -------------------
 dd if=output/images/rootfs.iso9660 of=/dev/sdb