remove duplicate entry "哼".

Line 6572: 哼	heng	2072
Line 7033: 哼	heng	2072

This suppress the following warning:
> entry_collector.cc:194] duplicate word definition '哼': [heng].
Merge pull request #79 from pallxk/master

remove duplicate entry "哼" of "pinyin_simp.dict.yaml".