drivers: wifi: esp_at: don't send AT+CWLAP during initial setup

Sending AT+CWLAP was introduced with commit f2859f95 ("drivers:
wifi: esp_at: changes to scanning") as a way to easily test introduced
changes, rather than on purpose. Remove that now, as there is no
particular reason to send it and additionally it breaks setup phase:

  <err> modem_cmd_handler: command AT+CWLAP ret:-5
  <err> wifi_esp_at: Init failed -5

with ESP-AT firmware v2.1.

Signed-off-by: Marcin Niestroj <m.niestroj@grinn-global.com>