Because

The order of instructions in the hashmap lesson may lead to confusion over the process of overwriting values if the key already exists in the map.

This PR

• Rearranges the instructions on overwriting values so that confusion is removed and the lesson flows better.
• Removes unnecessary bullet about adding a Node as it's irrelevant to the process of retrieving a value from the map

Issue

Closes #27982

Additional Information

Pull Request Requirements

• I have thoroughly read and understand The Odin Project curriculum contributing guide
• The title of this PR follows the location of change: brief description of change format, e.g. Intro to HTML and CSS lesson: Fix link text
• The Because section summarizes the reason for this PR
• The This PR section has a bullet point list describing the changes in this PR
• If this PR addresses an open issue, it is linked in the Issue section
• If any lesson files are included in this PR, they have been previewed with the Markdown preview tool to ensure it is formatted correctly
• If any lesson files are included in this PR, they follow the Layout Style Guide