docs: driver-api: address duplicate label warning

Delete identically named subsection to fix Documentation warning:

Documentation/driver-api/w1.rst:11: \
WARNING: duplicate label driver-api/w1:w1 api internal to the kernel, \
other instance in Documentation/driver-api/w1.rst

Signed-off-by: Lukas Bulwahn <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Jonathan Corbet <[e-mail]>

Documentation/driver-api/w1.rst

···
 W1 API internal to the kernel
 =============================
 
-W1 API internal to the kernel
------------------------------
-
 include/linux/w1.h
 ~~~~~~~~~~~~~~~~~~