MAINTAINERS: remove obsolete pattern in RTC SUBSYSTEM section

MAINTAINERS: remove obsolete pattern in RTC SUBSYSTEM section

Commit d890cfc25fe9 ("rtc: ds2404: Convert to GPIO descriptors") removes
the rtc-ds2404.h platform data and with that, there is no file remaining
matching the pattern 'include/linux/platform_data/rtc-*'. Hence,
./scripts/get_maintainer.pl --self-test=patterns complains about a broken
reference.

Remove the obsolete file pattern in the REAL TIME CLOCK (RTC) SUBSYSTEM.

Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/r/20230825053910.17941-1-lukas.bulwahn@gmail.com
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>