[cleanup] Remove internally deprecated default class not used

All this does is waste memory on the license-maven-plugin-fs test that uses it.

The adjustProperties fails to use what it created there so that just goes to GC.

The deprecated method only returns Collections.emptyMap().

Due to test in the license-maven-plugin-fs, keep these as default but have them do nothing as that is what they are actually doing.  The adjustProperties will remain to send back emptyMap()

license-maven-plugin/src/main/java/com/mycila/maven/plugin/license/PropertiesProvider.java

@@ -20,35 +20,18 @@
 import java.io.Closeable;
 import java.util.Collections;
 import java.util.Map;
-import java.util.Properties;
 
 /**
  */
 public interface PropertiesProvider extends Closeable {
 
   default void init(AbstractLicenseMojo mojo, Map<String, String> currentProperties) {
+      // Do nothing on default
   }
 
   default Map<String, String> adjustProperties(AbstractLicenseMojo mojo,
                                                Map<String, String> currentProperties, Document document) {
-    Properties properties = new Properties();
-    properties.putAll(currentProperties);
-    return getAdditionalProperties(mojo, properties, document);
-  }
-
-  /**
-   * Gets the additional properties.
-   *
-   * @param mojo              the maven mojo
-   * @param currentProperties the current properties
-   * @param document          the document to process
-   * @return the additional properties
-   *
-   * @deprecated Use instead {@link #adjustProperties(AbstractLicenseMojo, Map, Document)}
-   */
-  @Deprecated
-  default Map<String, String> getAdditionalProperties(AbstractLicenseMojo mojo,
-                                                      Properties currentProperties, Document document) {
+    // Return empty collection on default
     return Collections.emptyMap();
   }