Making deepslate generate below y=0, not y=16 (#1433)

* Fixes #1431

* Updating carpet rule description

* Making it work for cobbled deepslate

src/main/java/carpet/CarpetSettings.java

@@ -877,8 +877,7 @@ public class CarpetSettings
     public static boolean renewableBlackstone = false;
 
     @Rule(
-            desc = "Lava and water generate deepslate and cobbled deepslate instead below Y16",
-            extra = "This rule may change Y value to 0 with 1.18",
+            desc = "Lava and water generate deepslate and cobbled deepslate instead below Y0",
             category = FEATURE
     )
     public static boolean renewableDeepslate = false;