Fix sonar warnings

src/main/java/org/itsallcode/luava/FunctionCallException.java

@@ -1,7 +1,7 @@
 package org.itsallcode.luava;
 
+@SuppressWarnings("serial")
 public class FunctionCallException extends LuaException {
-    private static final long serialVersionUID = 1L;
     private final String function;
     private final int errorCode;
     private final String message;

src/main/java/org/itsallcode/luava/LuaException.java

@@ -1,8 +1,7 @@
 package org.itsallcode.luava;
 
+@SuppressWarnings("serial")
 public class LuaException extends RuntimeException {
-    private static final long serialVersionUID = 1L;
-
     public LuaException(final String message) {
         super(message);
     }

src/main/java/org/itsallcode/luava/LuaType.java

@@ -11,7 +11,7 @@ public enum LuaType {
 
     private final int type;
 
-    private LuaType(final int type) {
+    LuaType(final int type) {
         this.type = type;
     }