Documentation/CodingStyle: Fix duplicate "are" typo

The improved paragraph about line lengths contains a sentence with a
duplicate word: there is one "are" at the end of a line, followed by a
second one at the beginning of the next line.

Drop the first one, as that one is part of the longest line.

Fixes: bdc48fa1

 ("checkpatch/coding-style: deprecate 80-column warning")
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>