MDL-46451 mod_lti: Fix restoring old float grades

LTI's activity table used to have a float
field for the grade.  Now it is an integer
so we must restore the grade as an integer
so it matches the table schema.

mod/lti/backup/moodle2/restore_lti_stepslib.php

@@ -74,6 +74,9 @@ class restore_lti_activity_structure_step extends restore_activity_structure_ste
         $data->course = $this->get_courseid();
         $data->servicesalt = uniqid('', true);
 
+         // Grade used to be a float (whole numbers only), restore as int.
+        $data->grade = (int) $data->grade;
+
         // Clean any course or site typeid. All modules
         // are restored as self-contained. Note this is
         // an interim solution until the issue below is implemented.