MDL-80043 gradereport_grader: No need to pass header parameter

No need to pass a value for the header parameter in
print_grade_page_head() because:
1. The default grade plugin name will be used anyway.
2. It will allow the use of the editingmode_title lang string for the
grader report so the page title can reflect the display mode of the
grader report, especially when editing mode is turned on.

grade/report/grader/index.php

@@ -107,13 +107,11 @@
     grade_report_grader::do_process_action($target, $action, $courseid);
 }
 
-$reportname = get_string('pluginname', 'gradereport_grader');
-
 // Do this check just before printing the grade header (and only do it once).
 grade_regrade_final_grades_if_required($course);
 
 // Print header
-print_grade_page_head($COURSE->id, 'report', 'grader', $reportname, false, $buttons);
+print_grade_page_head($COURSE->id, 'report', 'grader', false, false, $buttons);
 
 //Initialise the grader report object that produces the table
 //the class grade_report_grader_ajax was removed as part of MDL-21562