typo

[HannanKan]

In assignment website https://zfhu.ac.cn/PRML-Spring19-Fudan/assignment-2/index.html
Given function "gen_linear_seperatable_2d_2c_dataset" should be "get_linear_seperatable_2d_2c_dataset"

[ichn-hu]

Thank you for figure out this typo, could you please fix it and propose a pull request and I will merge it.