fix: [M3-8572] - Scrollbar showing briefly on Splash Screen

[bnussman-akamai]

Description 📝

• Fixes bug where a scrollbar would briefly show on the splash screen due to missing sr-only css class 📄

Preview 📷

Before	After
Screen.Recording.2024-09-11.at.1.53.01.PM.mov	Screen.Recording.2024-09-11.at.1.52.35.PM.mov

How to test 🧪

• Verify you don't see a scrollbar on the initial load of Cloud Manager
• If you want the splash screen to stay open for testing, go to line 30 of App.tsx and force the splash screen to stay open

As an Author I have considered 🤔

• 👀 Doing a self review
• ❔ Our contribution guidelines
• 🤏 Splitting feature into small PRs
• ➕ Adding a changeset
• 🧪 Providing/Improving test coverage
• 🔐 Removing all sensitive information from the code and PR description
• 🚩 Using a feature flag to protect the release
• 👣 Providing comprehensive reproduction steps
• 📑 Providing or updating our documentation
• 🕛 Scheduling a pair reviewing session
• 📱 Providing mobile support
• ♿ Providing accessibility support

[github-actions]

Coverage Report: ✅
Base Coverage: 86.64%
Current Coverage: 86.64%