fix:恢复了findCourseById的内容

seecoder-portal-server/src/main/java/cn/seecoder/seecoderportalserver/web/rest/CourseController.java

@@ -19,7 +19,7 @@ public class CourseController {
 
     @GetMapping("/getCourseById")
     public OkResponse<CourseVO> findCourseById(@RequestParam Long id) {
-        return null;
+        return OkResponse.of(courseService.findCourseById(id));
     }
 
     @PostMapping("/create")