Fix bounds on delete_ith

[actuallyatiger]

Pull Request Template

Description

Fixes #879
Updates the out-of-bounds check to include length = index and also adjusts the bound on the call to delete_tail so that it can actually be used.

Also added a test case for when length = index

Type of change

• Bug fix (non-breaking change which fixes an issue)

Checklist:

• I ran bellow commands using the latest version of rust nightly.
• I ran cargo clippy --all -- -D warnings just before my last commit and fixed any issue that was found.
• I ran cargo fmt just before my last commit.
• I ran cargo test just before my last commit and all tests passed.
• I checked COUNTRIBUTING.md and my code follows its guidelines.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 95.51%. Comparing base (a45a382) to head (1f885db).

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #880      +/-   ##
==========================================
+ Coverage   95.50%   95.51%   +0.01%     
==========================================
  Files         317      317              
  Lines       22948    22955       +7     
==========================================
+ Hits        21916    21925       +9     
+ Misses       1032     1030       -2     

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