Made deepslate generate below y16 (#914)

* Made deepslate generate below y16

* Update src/main/java/carpet/CarpetSettings.java

Co-authored-by: gnembon <41132274+gnembon@users.noreply.github.com>

src/main/java/carpet/CarpetSettings.java

@@ -769,7 +769,8 @@ public class CarpetSettings
     public static boolean renewableBlackstone = false;
 
     @Rule(
-            desc = "Lava and water generate deepslate and cobbled deepslate instead below y0",
+            desc = "Lava and water generate deepslate and cobbled deepslate instead below Y16",
+            extra = "This rule may change Y value to 0 with 1.18",
             category = FEATURE
     )
     public static boolean renewableDeepslate = false;