MAINTAINERS: Drop entries for hwmon devices with unreachable maintainers

Drop maintainer entries for MAX31760 and MAX31827 since the e-mail
addresses of their maintainers is no longer reachable and there is
no known alternative means to contact them.

HWMON drivers have a subsystem maintainer, so individual maintainer
entries are not mandatory.

Reported-by: Heiner Kallweit <hkallweit1@gmail.com>
Cc: Heiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>