platform/x86: thinkpad_acpi: remove obsolete TODO comment

platform/x86: thinkpad_acpi: remove obsolete TODO comment

This patch removes the obsolete TODO comment regarding fan speed
presets in fan_write_cmd_speed. After discussion with the
maintainers, it was decided that fixed presets (low/medium/high)
are not suitable due to platform-specific variations.

Signed-off-by: Daniil Bulgar <bulgardaniil18@gmail.com>
Reviewed-by: Mark Pearson <mpearson-lenovo@squebb.ca>
Link: https://patch.msgid.link/20260407190546.109900-1-bulgardaniil18@gmail.com
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>