Hashmap Project: Specify initial capacity

[kensulite]

Because

When testing their project, learners are asked to create a Hashmap with a load factor of 0.75, but never in the assignment they are informed about needing an initial capacity size of 16 for this.

This PR

• Updates the JavaScript Hashmap project lesson to inform learners that a Hashmap with a load factor of 0.75 should have an initial capacity size of 16.
• Updates the Ruby Hashmap project lesson to inform learners that a Hashmap with a load factor of 0.75 should have an initial capacity size of 16.

Issue

Closes #29162

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

[01zulfi]

lgtm