twister: add space in custom_flash_scripts example and test

This makes sure parsers don't trip over whitespace (as many do).

I suggested this late in #93944

Signed-off-by: Marc Herbert <[email protected]>

Author: marc-hb

doc/develop/test/twister.rst

@@ -1456,19 +1456,19 @@ in a hardware map.
       .. code-block:: bash
 
          twister -p npcx9m6f_evb --device-testing --device-serial /dev/ttyACM0
-         --flash-command './custom_flash_script.py,--flag,"complex,argument"'
+         --flash-command './custom_flash_script.py,--flag,"complex, argument"'
 
    .. group-tab:: Windows
 
       .. note::
 
          python .\scripts\twister -p npcx9m6f_evb --device-testing
          --device-serial COM1
-         --flash-command 'custom_flash_script.py,--flag,"complex,argument"'
+         --flash-command 'custom_flash_script.py,--flag,"complex, argument"'
 
 Would result in calling ``./custom_flash_script.py
 --build-dir <build directory> --board-id <board identification>
---flag complex,argument``.
+--flag "complex, argument"``.
 
 Fixtures
 +++++++++

scripts/tests/twister/test_handlers.py

@@ -1157,9 +1157,9 @@ def mock_availability(handler, instance, no=num_of_failures):
         None,
         None,
         None,
-        'path to/flash_command,with,args,"1,2,3",4',
+        'path to/flash_command,with,args,"1, 2, 3",4',
         ['path to/flash_command', '--build-dir', '$build_dir', '--board-id',
-         12345, 'with', 'args', '1,2,3', '4']
+         12345, 'with', 'args', '1, 2, 3', '4']
     ),
 ]