Revert custom serialisation of UnhandledAlertException

I'm not sure why this was added, and the commit it landed in
doesn't explain why the change was made. Reverting, since it
appears to be unnecessary.

java/client/src/org/openqa/selenium/UnhandledAlertException.java

@@ -17,9 +17,6 @@
 
 package org.openqa.selenium;
 
-import com.google.gson.JsonObject;
-import com.google.gson.JsonPrimitive;
-
 public class UnhandledAlertException extends WebDriverException {
 
   private final String alertText;
@@ -39,12 +36,4 @@ public UnhandledAlertException(String message, String alertText) {
   public String getAlertText() {
     return alertText;
   }
-
-  public JsonObject toJson() {
-    JsonObject text = new JsonObject();
-    text.add("text", new JsonPrimitive(alertText));
-    JsonObject alert = new JsonObject();
-    alert.add("alert", text);
-    return alert;
-  }
 }

java/client/test/org/openqa/selenium/remote/BeanToJsonConverterTest.java

@@ -17,6 +17,15 @@
 
 package org.openqa.selenium.remote;
 
+import static org.hamcrest.Matchers.containsString;
+import static org.hamcrest.Matchers.is;
+import static org.hamcrest.Matchers.not;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertThat;
+import static org.junit.Assert.assertTrue;
+import static org.junit.Assert.fail;
+
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableMap;
 import com.google.common.collect.Lists;
@@ -32,7 +41,6 @@
 import org.openqa.selenium.Cookie;
 import org.openqa.selenium.Platform;
 import org.openqa.selenium.Proxy;
-import org.openqa.selenium.UnhandledAlertException;
 import org.openqa.selenium.WebDriverException;
 import org.openqa.selenium.logging.LogEntries;
 import org.openqa.selenium.logging.LogEntry;
@@ -49,15 +57,6 @@
 import java.util.concurrent.TimeUnit;
 import java.util.logging.Level;
 
-import static org.hamcrest.Matchers.containsString;
-import static org.hamcrest.Matchers.is;
-import static org.hamcrest.Matchers.not;
-import static org.junit.Assert.assertEquals;
-import static org.junit.Assert.assertFalse;
-import static org.junit.Assert.assertThat;
-import static org.junit.Assert.assertTrue;
-import static org.junit.Assert.fail;
-
 
 @RunWith(JUnit4.class)
 public class BeanToJsonConverterTest {
@@ -328,12 +327,6 @@ public void testShouldBeAbleToConvertAWebDriverException() {
     verifyStackTraceInJson(raw, stackTrace);
   }
 
-  @Test
-  public void testShouldConverUnhandledAlertException() {
-    RuntimeException clientError = new UnhandledAlertException("unhandled alert", "cheese!");
-    assertEquals("{\"alert\":{\"text\":\"cheese!\"}}", new BeanToJsonConverter().convert(clientError));
-  }
-
   @Test
   public void testShouldConvertDatesToMillisecondsInUtcTime() {
     String jsonStr = new BeanToJsonConverter().convert(new Date(0));