[xdata] Remove FormWriter

The FormWriter interface was a left over from the initial design of
the reworked API, but is no longer required.

smack-extensions/src/main/java/org/jivesoftware/smackx/xdata/form/FillableForm.java

@@ -39,7 +39,7 @@ import org.jxmpp.jid.util.JidUtil;
 import org.jxmpp.stringprep.XmppStringprepException;
 import org.jxmpp.util.XmppDateTime;
 
-public class FillableForm extends FilledForm implements FormWriter {
+public class FillableForm extends FilledForm {
 
     private final Set<String> requiredFields;
 
@@ -212,7 +212,6 @@ public class FillableForm extends FilledForm implements FormWriter {
         write(filledFormField);
     }
 
-    @Override
     public final void write(FormField filledFormField) {
         if (filledFormField.getType() == FormField.Type.fixed) {
             throw new IllegalArgumentException();

smack-extensions/src/main/java/org/jivesoftware/smackx/xdata/form/FormWriter.java

@@ -1,25 +0,0 @@
-/**
- *
- * Copyright 2020 Florian Schmaus
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-package org.jivesoftware.smackx.xdata.form;
-
-import org.jivesoftware.smackx.xdata.FormField;
-
-public interface FormWriter {
-
-    void write(FormField field);
-
-}