Remove unused code and file, and add a .luacheckrc

.luacheckrc

@@ -0,0 +1,12 @@
+read_globals = {
+	minetest = {
+		fields = {
+			registered_entities = {
+				read_only = false,
+				other_fields = true
+			}
+		},
+		other_fields = true
+	},
+	"vector"
+}

LICENSE.txt

@@ -1,3 +1,2 @@
 MIT for the code
-CC-BY 4.0 for the sound
 The original mod was licensed under WTFPL.

init.lua

@@ -1,11 +1,7 @@
 -- Use the movement gravity for the downwards acceleration.
 -- The setting may change in-game but for simplicity we don't support this.
-local movement_gravity = tonumber(core.settings:get("movement_gravity")) or 9.81
-
-local function is_flowing_liquid(nodename)
-	local def = minetest.registered_nodes[nodename]
-	return def and def.liquidtype == "flowing"
-end
+local movement_gravity = tonumber(minetest.settings:get("movement_gravity"))
+	or 9.81
 
 -- get_flow_raw determines the horizontal flow vector for a flowing liquid node,
 -- or returns nothing if the flow is zero