fix: Fix stylesheet

[saforem2]

Description

Screenshots (if applicable)

Before

After

Related Issue(s)

Type of Change

• Documentation content update (new page, formatting/typo changes, adding more info, etc.)
• Functionality bug fix
• New feature (mkdocs feature, mkdocs-material style changes, HTML/CSS/JS customization, developer or repo tool)

Checklist

• I have run make serve or make build-docs locally and verified that my changes render correctly
• I have added at least one Label to this PR

[Copilot]

Pull Request Overview

This PR fixes and cleans up the CSS stylesheet for the ALCF documentation theme. The changes focus on updating color variables and removing commented-out code for better maintainability.

• Updates color variables from green/neutral colors to blue/med colors in navigation and code highlighting
• Removes commented-out CSS rules and adds new commented placeholders for future customization
• Reorganizes code background color property placement for better readability

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[atanikan]

LGTM