delete the deadline of exercise submission and course exam

There is no deadline of exercise submission and course exam according to the latest course policy, but the Chinese version material has not been revised yet.

src/content/0/zh/part0a.md

@@ -45,11 +45,8 @@ lang: zh
 <!-- In parts 1-4 you are expected to do <i>at least</i> all of the exercises that are not marked with an asterisk(*). Exercises marked with an asterisk count towards your final grade, but skipping them does not prevent you from doing the compulsory exercises in the next parts. Parts 5- do not have asterisk marked exercises since there is no similar dependency on previous parts.-->
 在第 1-4 章中，你应该<i>至少</i>做完所有没有标有星号（*）的练习。标有星号的练习虽然计入你的最终成绩，但跳过这些练习并不妨碍你做下一章节的必修练习。第5章节没有标有星号的练习，因为与前几章节没有类似的依赖关系。
 
-<!-- The speed of completing the course is flexible, and exercises can be submitted until 23:59 [EET](https://en.wikipedia.org/wiki/Eastern_European_Time) on 1 March 2023.-->
-完成课程的速度是灵活的，练习可以提交到2023年3月1日23:59 [东欧时间EET](https://en.wikipedia.org/wiki/Eastern_European_Time)。
-
-<!-- However, note that the deadline for taking exam for University of Helsinki credits is 10.1.2023.-->
-然而，请注意参加赫尔辛基大学学分考试的最后期限是2023年1月10日。
+<!-- The speed of completing the course is flexible.-->
+完成课程的速度是灵活的。
 
 <!-- Exercise completion time statistics can be found via the [submission system](https://studies.cs.helsinki.fi/stats/courses/fullstackopen).-->
 练习完成时间的统计可以通过[提交系统](https://studies.cs.helsinki.fi/stats/courses/fullstackopen)找到。