docs: userspace: ioctl-number: remove mc146818rtc conflict

In 2.3.43pre2, the RTC ioctls definitions were actually moved from
linux/mc146818rtc.h to linux/rtc.h
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20200209203304.66004-1-alexandre.belloni@bootlin.comSigned-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/userspace-api/ioctl/ioctl-number.rst

@@ -266,7 +266,6 @@ Code  Seq#    Include File                                           Comments
 'o'   01-A1  `linux/dvb/*.h`                                         DVB
 'p'   00-0F  linux/phantom.h                                         conflict! (OpenHaptics needs this)
 'p'   00-1F  linux/rtc.h                                             conflict!
-'p'   00-3F  linux/mc146818rtc.h                                     conflict!
 'p'   40-7F  linux/nvram.h
 'p'   80-9F  linux/ppdev.h                                           user-space parport
                                                                      <mailto:tim@cyberelk.net>