docs: hwmon: sysfs-interface: Fix stray colon

docs: hwmon: sysfs-interface: Fix stray colon

The commit 036d6a4e75c9 ("ABI: sysfs-class-hwmon: add ABI documentation
for it") moved all ABI attributes to the usual ABI documentation. But this
change left a stray colon for the fan speed control method. Fix this
to avoid a confusion of readers.

Fixes: 036d6a4e75c9 ("ABI: sysfs-class-hwmon: add ABI documentation for it")
Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>
Link: https://lore.kernel.org/r/20230312155714.17290-1-stefan.wahren@i2se.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>