refer to a few instruction to setup RPi as the WiFi AP, here is how to remove it.

reverse RPi WiFi AP.md

Remove the packages

sudo apt purge hostapd dnsmasq

Remove all settings

if these setting files are existed, here is how to roll back

/etc/dhcpcd.conf

remove denyinterfaces xxxx

/etc/network/interfaces

remove all lines under iface xxxx inet static, sample

allow-hotplug wlan0
iface wlan0 inet static
    address 192.168.5.1
    netmask 255.255.255.0
    network 192.168.5.0
    broadcast 192.168.5.255

/etc/hostapd/hostapd.conf

delete this file

/etc/default/hostapd

comment out this line DAEMON_CONF="/etc/hostapd/hostapd.conf"

/etc/dnsmasq.conf

delete this file

Reboot your RPi