How to delete all odd lines
ref: https://jingyan.baidu.com/article/fea4511ad3b199f7bb9125ba.html
1:%normal jkdd # even lines from current line (current line is 0)2:%normal jdd # odd lines
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ref: https://jingyan.baidu.com/article/fea4511ad3b199f7bb9125ba.html
1:%normal jkdd # even lines from current line (current line is 0)2:%normal jdd # odd lines