fix: quiz result email contains markdown (resolve #1790)

[jobara]

Resolve #1790

Replaces markdown syntax with HTML in email template for quiz results.

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 #1791 (1e61a5a) into dev (b479390) will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##                dev    #1791   +/-   ##
=========================================
  Coverage     96.47%   96.47%           
  Complexity     1984     1984           
=========================================
  Files           299      299           
  Lines          8636     8636           
=========================================
  Hits           8332     8332           
  Misses          304      304