fix: course styling and text updates (resolves #1870, #1872)

[jobara]

Resolves #1870
Resolves #1872

• Corrects module card typography to use an <h3> for the card heading
• Corrects module cards layout to use a 2 column grid
• Shortens the quiz's back button text

Prerequisites

If this PR changes PHP code or dependencies:

• I've run composer format and fixed any code formatting issues.
• I've run composer analyze and addressed any static analysis issues.
• I've run php artisan test and ensured that all tests pass.
• I've run composer localize to update localization source files and committed any changes.

If this PR changes CSS or JavaScript code or dependencies:

• I've run npm run lint and fixed any linting issues.
• I've run npm run build and ensured that CSS and JavaScript assets can be compiled.

[codecov]

Codecov Report

Merging #1873 (778489a) into dev (5c9fd55) will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##                dev    #1873   +/-   ##
=========================================
  Coverage     96.28%   96.28%           
  Complexity     2033     2033           
=========================================
  Files           301      301           
  Lines          8756     8756           
=========================================
  Hits           8431     8431           
  Misses          325      325