Fix Netherite not working for certain skills (like Skull Splitter)

pom.xml

@@ -2,7 +2,7 @@
     <modelVersion>4.0.0</modelVersion>
     <groupId>com.gmail.nossr50.mcMMO</groupId>
     <artifactId>mcMMO</artifactId>
-    <version>2.1.137</version>
+    <version>2.1.138-SNAPSHOT</version>
     <name>mcMMO</name>
     <url>https://github.com/mcMMO-Dev/mcMMO</url>
     <scm>

src/main/java/com/gmail/nossr50/util/skills/CombatUtils.java

@@ -980,6 +980,8 @@ public final class CombatUtils {
         }
         else if (ItemUtils.isDiamondTool(inHand)) {
             tier = 4;
+        } else if (ItemUtils.isNetheriteTool(inHand)) {
+            tier = 5;
         }
         else if (mcMMO.getModManager().isCustomTool(inHand)) {
             tier = mcMMO.getModManager().getTool(inHand).getTier();