[nrf fromlist] tests: drivers: watchdog: align to wdt_nrfx rework

Removed unnecessary symbol.

Upstream PR #: 96776

Signed-off-by: Michał Stasiak <[email protected]>

Author: mstasiaknordic

tests/drivers/watchdog/wdt_basic_api/boards/nrf52840dk_nrf52840_counter.conf

@@ -1,4 +1,3 @@
 # Disable hardware watchdog
 CONFIG_WDT_NRFX=n
-CONFIG_NRFX_WDT0=n
 CONFIG_ZERO_LATENCY_IRQS=y