samples: drivers: rtc application runs on stm32f3_disco target

Check that rtc has, at least, incremented second counter
one time to validated the sample.

Signed-off-by: Francois Ramu <francois.ramu@st.com>

samples/drivers/rtc/README.rst

@@ -27,8 +27,7 @@ Sample Output
 
 .. code-block:: console
 
-   RTC date and time: 2024-11-17 04:21:47
-   RTC date and time: 2024-11-17 04:21:48
-   RTC date and time: 2024-11-17 04:21:49
+   RTC date and time: 2024-11-17 04:19:00
+   RTC date and time: 2024-11-17 04:19:01
 
    <repeats endlessly>

samples/drivers/rtc/sample.yaml

@@ -4,9 +4,16 @@ tests:
   sample.drivers.rtc:
     platform_allow:
       - stm32f3_disco
+    integration_platforms:
+      - stm32f3_disco
     tags:
       - samples
       - rtc
       - api
     depends_on:
       - rtc
+    harness: console
+    harness_config:
+      type: one_line
+      regex:
+        - "RTC date and time: 2024-11-17 04:19:01"