New Google Drive link for poster dataset

[ginazhouhuiwu]

Hosting new dataset here.

Addresses #3044

[brentyi]

also fixes #2959!

[edwardchenomni]

Hi, thanks for your works!
But I found that the zip file you provided may cause another problem.
in your zip file, there exist not only the expected 'poster' folder but also a '__MACOSX' folder.
This triggers the assertion error at this line.
Moreover, depends on the runtime, the two folders may switch order, which in turn cause problem on the next line.