Fix YAML representation of backlight colour.

The YAML representation was a string, not a list of integers, so it
broke whilst trying to insert into the payload.

Author: gerph

res/themes/3.5inchTheme2_theme/theme.yaml

@@ -4,7 +4,7 @@ display:
   DISPLAY_ORIENTATION: portrait
 
   # Backplate RGB LED color (for HW revision 'flagship' devices only)
-  DISPLAY_RGB_LED: 0, 0, 255
+  DISPLAY_RGB_LED: [0, 0, 255]
 
 static_images:
   # Specify what static images we want to show on the display
@@ -298,4 +298,4 @@ STATS:
         FONT_SIZE: 23
         FONT_COLOR: 255, 255, 255
         BACKGROUND_COLOR: 132, 154, 165
-        # BACKGROUND_IMAGE: background.png
+        # BACKGROUND_IMAGE: background.png