Remove package building from Day 5 materials

[ryoliver]

Students are asked to build a bare-bones package during Day 5 to:

1. reinforce function documentation (introduced during Day 5)
2. and reinforce the concept that packages are just collections of functions

Propose eliminating this material for the following reasons:

1. Students typically run into issues that are challenging debug on the fly
2. Package creation is not revisited later in the curriculum

Instead, it would be beneficial to do more practice on sourcing functions and scripts. This is a more foundational concept to creating workflows and is conceptually challenging for many students.