remove unused ird_color_dead_block_background

ir/ir/irdump.c

@@ -50,7 +50,6 @@ typedef enum ird_color_t {
 	ird_color_none = -1,
 	ird_color_prog_background,
 	ird_color_block_background,
-	ird_color_dead_block_background,
 	ird_color_block_inout,
 	ird_color_default_node,
 	ird_color_phi,
@@ -273,7 +272,6 @@ static void init_colors(void)
 
 	custom_color(ird_color_prog_background,  "204 204 204");
 	custom_color(ird_color_block_background, "255 255 0");
-	custom_color(ird_color_dead_block_background, "190 150 150");
 	named_color(ird_color_block_inout,       "lightblue");
 	named_color(ird_color_default_node,      "white");
 	custom_color(ird_color_memory,           "153 153 255");