how to delete the nth line in a multiline string?

How do I delete the $ n$ th line in a multi-line string.

For example how would I delete the $ 2$ nd line in the following string?

multiLineString = "line 1\nline 2\nline 3\nline 4"; 

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such that the output is

"line 1\nline 3\nline 4" 

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