Removes icon unit test. (#8370)

"Random" unit test failures appear to be a long-existing BYOND issue (~4 years at least). If I figure out how to solve this I'll resubmit... (unlikely)

We can keep in the various icon fixes from the PR that added this test.

code/unit_tests/icon_tests.dm

@@ -1,38 +0,0 @@
-/datum/unit_test/icon_test
-	name = "ICON STATE template"
-
-/datum/unit_test/icon_test/all_initial_icon_states_shall_exist
-	name = "ICON STATE - All initial icon states shall exist"
-	var/list/excepted_atoms = list() // Any specific atoms that should not be included
-	var/list/excepted_icon_files = list() //Contains any .dmi files you do not want this test to run on
-	var/list/excepted_icon_states = list() //Any individual icon states you do not want this test to run on
-
-/datum/unit_test/icon_test/all_initial_icon_states_shall_exist/start_test()
-	var/list/failed_icons = list()
-
-	for(var/atom_type in (subtypesof(/atom) - excepted_atoms))
-		var/failed = FALSE
-		var/atom/test_atom = atom_type
-
-		var/atom_icon = initial(test_atom.icon)
-		if(atom_icon in excepted_icon_files)
-			continue
-		if(atom_icon)
-			var/atom_icon_state = initial(test_atom.icon_state)
-			if(!atom_icon_state || (atom_icon_state in excepted_icon_states))
-				continue
-
-			var/list/valid_states = icon_states(atom_icon)
-			if(!(atom_icon_state in valid_states))
-				failed = TRUE
-				log_unit_test("[ascii_red]--------------- [atom_type] - Icon state [atom_icon_state] was not found in [atom_icon].")
-
-		if(failed)
-			failed_icons += atom_type
-
-	if(LAZYLEN(failed_icons))
-		fail("[LAZYLEN(failed_icons)] atom initial icons were not found.")
-	else
-		pass("All atom initial icons were valid.")
-
-	return TRUE