Make AbstractLocation a sealed class

Seal AbstractLocation to explicitly declare its only permitted subclasses
(Billing and Shipping). This makes the type hierarchy more explicit and
enables better pattern matching and exhaustiveness checking in Java 17+.

Note: MinFraudException was already using sealed classes.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

Author: oschwald

src/main/java/com/maxmind/minfraud/request/AbstractLocation.java

@@ -7,7 +7,8 @@
 /**
  * This class represents the shared location behavior between Billing and Shipping.
  */
-public abstract class AbstractLocation extends AbstractModel {
+public abstract sealed class AbstractLocation extends AbstractModel
+    permits Billing, Shipping {
     private final String firstName;
     private final String lastName;
     private final String company;