Update readme_cn.md misspelling (#2088)

learningpro

2024-09-20 8c88d71f34ddf78588983538f887b8fb483996cd

1
2
3
4
5
6
7
8
p m    p.m.
pm    p.m.
p.m.
p.m    p.m.
am    a.m.
a.m.
a.m    a.m.
a m    a.m.