Bluetooth: Samples: Remove usage of `BT_DEBUG_LOG`

Remove usage of Kconfig symbol `CONFIG_BT_DEBUG_LOG` from samples. It
has been deprecated since this PR:
https://github.com/zephyrproject-rtos/zephyr/pull/56183



The Kconfig symbols has been replaced by `CONFIG_LOG=y` on most of the
cases. Or it has been removed when not needed anymore.

Signed-off-by: Théo Battrel <theo.battrel@nordicsemi.no>