fix(examples): use 'n' instead of '0'/'false' for bool Kconfig defaults

'0' and 'false' are not valid values for a bool symbol. The parser emits
a note and falls back to 'n', so the resulting configuration is correct
but the build is noisy. Set the two remaining example symbols to
'default n' to make the value explicit and silence the note.

examples/peripherals/twai/twai_utils/main/Kconfig.projbuild

@@ -6,7 +6,7 @@ menu "TWAI Configuration"
     config EXAMPLE_ENABLE_TWAI_FD
         bool "Enable TWAI-FD Support"
         depends on SOC_TWAI_FD_SUPPORTED
-        default false
+        default n
         help
             Enable TWAI-FD (Flexible Data-rate) support.
             Allows up to 64 bytes of data per frame and dual bit rates.