add flush to avoid hitting the duplicate constraint issue

Author: mightycox

api/src/main/java/ca/bc/gov/educ/api/pen/replication/service/TraxStudentCourseService.java

@@ -29,7 +29,8 @@ public void deletePriorAndSaveTraxStudentCourses(final List<TraxStudentCourseEnt
     try {
       if(!existingCourseList.isEmpty()) {
         log.info("Removing existing course list for PEN: {}", existingCourseList.get(0).getStudXcrseId().getStudNo());
-        this.traxStudentCourseRepository.deleteAll(existingCourseList);
+        this.traxStudentCourseRepository.deleteAllInBatch(existingCourseList);
+        this.traxStudentCourseRepository.flush();
       }
 
       if(!studentCourseEntityList.isEmpty()) {