Convert some bools to TRUE/FALSE instead of 1/0. (#11100)

Co-authored-by: Aronai Sieyes <arokha@arokha.com>

code/modules/persistence/filth.dm

@@ -5,7 +5,7 @@
 	icon_state = "mfloor1"
 	random_icon_states = list("mfloor1", "mfloor2", "mfloor3", "mfloor4", "mfloor5", "mfloor6", "mfloor7")
 	color = "#464f33"
-	anchored = 1
+	anchored = TRUE
 	persistent = TRUE
 
 /obj/effect/decal/cleanable/filth/Initialize()

code/modules/persistence/graffiti.dm

@@ -9,7 +9,7 @@
 	blend_mode = BLEND_MULTIPLY
 	color = "#000000"
 	alpha = 120
-	anchored = 1
+	anchored = TRUE
 
 	var/message
 	var/graffiti_age = 0

code/modules/persistence/noticeboard.dm

@@ -4,8 +4,8 @@
 	icon = 'icons/obj/stationobjs.dmi'
 	icon_state = "nboard00"
 	layer = ABOVE_WINDOW_LAYER
-	density = 0
-	anchored = 1
+	density = FALSE
+	anchored = TRUE
 	var/list/notices
 	var/base_icon_state = "nboard0"
 	var/const/max_notices = 5