remove 515 experiment stuff

code/_experiments.dm

@@ -3,12 +3,8 @@
 // Any flag you see here can be flipped with the `-D` CLI argument.
 // For example, if you want to enable EXPERIMENT_MY_COOL_FEATURE, compile with -DEXPERIMENT_MY_COOL_FEATURE
 
-// EXPERIMENT_515_QDEL_HARD_REFERENCE
-// - Hold a hard reference for qdeleted items, and check ref_count, rather than using refs. Requires 515+.
-
-// EXPERIMENT_515_DONT_CACHE_REF
-// - Avoids `text_ref` caching, aided by improvements to ref() speed in 515.
 
+/*
 #if DM_VERSION < 515
 
 	// You can't X-macro custom names :(
@@ -21,5 +17,6 @@
 #endif
 
 #if DM_VERSION >= 516
-	#error "Remove all 515 experiments"
+	#warn "Remove all 515 experiments"
 #endif
+*/