samples: net: wifi: Enable esp32 offload tests

The esp32 offload driver is used by shield esp_8266. This shield
doesn't have tests enabled to ensures that dependencies are ok.
This enables wifi sample to validate shield esp_8266 on CI and
consequently esp32 offload driver.

Fixes: #25386

Signed-off-by: Gerson Fernando Budke <nandojve@gmail.com>