VIM3 GPIOH6, H7 ERROR

I want to change GPIOH6 and GPIOH7 to output mode.
However, it is not changed with the command below.
Please confirm.

GPIOH6 & GPIOH7 are configured as uart by default.

Please edit /boot/env.txt to remove uart3 in overlays node, save & reboot the board to check again.