[nrf fromtree] tests: drivers: watchodg: Cleanup after nRF54LM20 rename

Remove duplicated test configuration after
nrf54l20pdk/nrf54l20/cpuxxx was renamed to
nrf54lm20dk/nrf54lm20a/cpuxxx.

Signed-off-by: Sebastian Głąb <[email protected]>
(cherry picked from commit a918256)

Author: nordic-segl

tests/drivers/watchdog/wdt_basic_api/boards/nrf54l20pdk_nrf54l20_cpuapp.overlay

@@ -10,11 +10,10 @@ tests:
     platform_allow:
       - nrf5340dk/nrf5340/cpuapp
       - nrf54l09pdk/nrf54l09/cpuapp
-      - nrf54l15dk/nrf54l15/cpuapp
-      - nrf54l20pdk/nrf54l20/cpuapp
-      - nrf54lm20dk/nrf54lm20a/cpuapp
       - nrf54h20dk/nrf54h20/cpuapp
       - nrf54h20dk/nrf54h20/cpurad
+      - nrf54l15dk/nrf54l15/cpuapp
+      - nrf54lm20dk/nrf54lm20a/cpuapp
       - nrf9280pdk/nrf9280/cpuapp
       - nrf9280pdk/nrf9280/cpurad
       - ophelia4ev/nrf54l15/cpuapp

tests/drivers/watchdog/wdt_error_cases/boards/nrf54l20pdk_nrf54l20_cpuapp.overlay

@@ -16,8 +16,8 @@ tests:
       - nrf54h20dk/nrf54h20/cpuppr
       - nrf54l09pdk/nrf54l09/cpuapp
       - nrf54l15dk/nrf54l15/cpuapp
-      - nrf54l20pdk/nrf54l20/cpuapp
       - nrf54lm20dk/nrf54lm20a/cpuapp
+      - nrf54lm20dk/nrf54lm20a/cpuflpr
       - ophelia4ev/nrf54l15/cpuapp
     integration_platforms:
       - nrf54l15dk/nrf54l15/cpuapp