samples: shell: Fix filtering for POSIX arch

One of these samples was filtering all POSIX arch
boards out by explictly listing them by name
(and for the nrf52_bsim by lack of UART).

Instead filter by the architecture.

There is no functional difference in tree with this change.

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

Author: aescolar

samples/subsys/shell/shell_module/sample.yaml

@@ -27,7 +27,7 @@ tests:
   sample.shell.shell_module.getopt:
     integration_platforms:
       - qemu_x86
-    platform_exclude: native_posix native_posix_64
+    arch_exclude: posix
     filter: CONFIG_SERIAL and dt_chosen_enabled("zephyr,shell-uart") and not CONFIG_NEWLIB_LIBC
     tags: shell
     harness: keyboard