Fix duplicate lines in multiline comments

[nielsdebruin]

What's changed?

Fixed a bug in parsing comments that caused duplicate linebreaks to be added to multiline comments using #.

Before the fix, the following test would fail, resulting in an output where an extra \n is added after each line starting with #

def test_multiline_comment_with_code():
    rewrite_run(python("""
    # This is a
    # multiline comment
    assert 1
    # This is another
    # multiline comment
    """))

Anyone you would like to review specifically?

@knutwannheden

Checklist

• I've added unit tests to cover both positive and negative cases
• I've read and applied the recipe conventions and best practices
• I've used the IntelliJ IDEA auto-formatter on affected files