tests/net/lib/lwm2m: Switch description to native_sim

native_posix is deprecated, let's switch the
description & comments to refer to native_sim instead.

Signed-off-by: Alberto Escolar Piedras <[email protected]>

Author: aescolar

tests/net/lib/lwm2m/interop/README.md

@@ -2,7 +2,7 @@
 
 This directory contains list of testcases that use
 the Twister's Pytest integration to run testcases against Leshan demo server.
-These tests use emulated hardware (native_posix).
+These tests use emulated hardware (native_sim).
 
 These tests require setup that is not done in Twister run, so follow this documentation to set
 up the test environment.
@@ -105,7 +105,7 @@ Install with `pip install CoAPthon3`
 ## Running tests
 
 ```
-twister -p native_posix -vv --enable-slow -T tests/net/lib/lwm2m/interop
+twister -p native_sim -vv --enable-slow -T tests/net/lib/lwm2m/interop
 ```
 
 Or use the Docker based testing

tests/net/lib/lwm2m/interop/pytest/leshan.py

@@ -420,7 +420,7 @@ def get_event_stream(self, endpoint: str, timeout: int = None):
         Events are notifications, updates and sends.
 
         The event stream must be closed after the use, so this must be used in 'with' statement like this:
-            with leshan.get_event_stream('native_posix') as events:
+            with leshan.get_event_stream('native_sim') as events:
                 data = events.next_event('SEND')
 
         If timeout happens, the event streams returns None.