Fix math rendering on blob pages

`renderGFM` adds the correct syntax highlighting class and triggers KaTeX if
required.

app/assets/javascripts/blob/viewer/index.js

@@ -111,7 +111,7 @@ export default class BlobViewer {
 
     BlobViewer.loadViewer(newViewer)
     .then((viewer) => {
-      $(viewer).syntaxHighlight();
+      $(viewer).renderGFM();
 
       this.$fileHolder.trigger('highlight:line');
       gl.utils.handleLocationHash();

changelogs/unreleased/33048-markdown-rendering-of-md-files-has-ceased-to-display-latex-equations.yml

+---
+title: Fix math rendering on blob pages
+merge_request:
+author: