docs/interop/firmware.json: Fix doc for FirmwareFlashMode

The doc title did not match the actual definition.

Fixes: 2720ceda05 ("docs: expand firmware descriptor to allow flash without NVRAM")
Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-ID: <20240307-qapi-firmware-json-v2-2-3b29eabb9b9a@linutronix.de>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>

docs/interop/firmware.json

@@ -223,7 +223,7 @@
 
 
 ##
-# @FirmwareFlashType:
+# @FirmwareFlashMode:
 #
 # Describes how the firmware build handles code versus variable
 # persistence.