fix(DLCMTestDocHelper): remove charset from content type

See https://github.com/spring-projects/spring-framework/issues/22788

DLCM-TestDocs/src/main/java/ch/dlcm/test/executor/DLCMTestDocHelper.java

@@ -3,7 +3,6 @@ package ch.dlcm.test.executor;
 import static org.hamcrest.CoreMatchers.endsWith;
 
 import java.io.UnsupportedEncodingException;
-import java.nio.charset.Charset;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;
@@ -25,9 +24,9 @@ import ch.dlcm.rest.ResourceName;
  */
 public class DLCMTestDocHelper {
 
-  public static final MediaType JSON_MEDIA_TYPE = new MediaType("application", "json", Charset.forName("UTF-8"));
-  public static final MediaType HAL_JSON_MEDIA_TYPE = new MediaType("application", "hal+json", Charset.forName("UTF-8"));
-  public static final MediaType HTML_MEDIA_TYPE = new MediaType("text", "html", Charset.forName("UTF-8"));
+  public static final MediaType JSON_MEDIA_TYPE = new MediaType("application", "json");
+  public static final MediaType HAL_JSON_MEDIA_TYPE = new MediaType("application", "hal+json");
+  public static final MediaType HTML_MEDIA_TYPE = new MediaType("text", "html");
 
   /* Applications routes */
   public static final String APPLICATION_ROOT = SolidifyConstants.URL_SEP;