v0.13 Fix double modify attribute. Closes #101

Author: hallahan

MapboxAndroidSDK/src/main/java/com/spatialdev/osm/model/OSMNode.java

@@ -140,9 +140,6 @@ public Marker getMarker() {
     @Override
     void xml(XmlSerializer xmlSerializer) throws IOException {
         xmlSerializer.startTag(null, "node");
-        if (isModified()) {
-            xmlSerializer.attribute(null, "action", "modify");
-        }
         setOsmElementXmlAttributes(xmlSerializer);
         xmlSerializer.attribute(null, "lat", String.valueOf(lat));
         xmlSerializer.attribute(null, "lon", String.valueOf(lng));