[nrf fromtree] tests: drivers: timer: nrf_grtc_timer: 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 afd90f4)

Author: nordic-segl

tests/drivers/timer/nrf_grtc_timer/testcase.yaml

@@ -2,20 +2,18 @@ tests:
   drivers.timer.nrf_grtc_timer:
     tags: drivers
     platform_allow:
+      - nrf54h20dk/nrf54h20/cpuapp
+      - nrf54h20dk/nrf54h20/cpurad
+      - nrf54h20dk/nrf54h20/cpuppr
       - nrf54l09pdk/nrf54l09/cpuapp
       - nrf54l09pdk/nrf54l09/cpuflpr
       - nrf54l15dk/nrf54l15/cpuapp
       - nrf54l15dk/nrf54l15/cpuflpr
       - nrf54l15bsim/nrf54l15/cpuapp
-      - nrf54h20dk/nrf54h20/cpuapp
-      - nrf54h20dk/nrf54h20/cpurad
-      - nrf54h20dk/nrf54h20/cpuppr
-      - nrf54l20pdk/nrf54l20/cpuapp
       - nrf54lm20dk/nrf54lm20a/cpuapp
-      - nrf54l20pdk/nrf54l20/cpuflpr
       - nrf54lm20dk/nrf54lm20a/cpuflpr
       - ophelia4ev/nrf54l15/cpuapp
       - ophelia4ev/nrf54l15/cpuflpr
     integration_platforms:
-      - nrf54l20pdk/nrf54l20/cpuapp
       - nrf54lm20dk/nrf54lm20a/cpuapp
+    timeout: 30