Fix Course Modal Styling

[a1-su]

Proposed Changes

This PR fixes the CSS styling so of the course modal. In particular, it ensures that the modal is now centred in the middle of the screen regardless of the screen width and height, and instead of the opaque black overlay, it is now a lighter gray.

Screenshots of your changes (if applicable)

Type of Change

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Type	Applies?
🚨 Breaking change (fix or feature that would cause existing functionality to change)
✨ New feature (non-breaking change that adds functionality)
🐛 Bug fix (non-breaking change that fixes an issue)	X
🎨 User interface change (change to user interface; provide screenshots)
♻️ Refactoring (internal change to codebase, without changing functionality)
🚦 Test update (change that only adds or modifies tests)
📦 Dependency update (change that updates a dependency)
🔧 Internal (change that only affects developers or continuous integration)

Checklist

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Questions and Comments

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[coveralls]

Pull Request Test Coverage Report for Build 4d05c0ba-e54d-472c-9270-8a59aa3b26a7

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 57.384%

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Totals
Change from base Build 52b7e702-2341-43fb-a92d-cde445f28de3:	0.0%
Covered Lines:	2316
Relevant Lines:	3945

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💛 - Coveralls

[david-yz-liu]

These are good, but please write them in alphabetical order in this set