Tree Offset logic is broken

[rohitrgupta]

Describe the bug
Offset always excludes more rows from the end as compared with the start of the list

Setup

To Reproduce
in the duckduckgoose example add following line after line 24
l.Offset(2, 1)

Current behavior
Duck
Duck

Expected behavior
Duck
Honk → Goose

Solution
The code for swapping the start and end values if start > end should be removed from the Tree Offset function