Handlebars syntax highlighting does not take affect

Summary

Configuring the file extensions for Handlebars syntax highlighting does not take affect and the text does not receive any highlighting. 

Steps to Reproduce

1. In bitbucket.properties add syntax.highlighter.text/x-handlebars-template.extensions=hbs
2. Restart Bitbucket Server
3. Add the below code to a test.hbs file, commit, and push it to a repository
4. Browse to the file

   {{> breadcrumbs}}
   
   {{!--
    You can use the t function to get
    content translated to the current locale, es:
    {{t 'article_list'}}
   --}}
   
   <h1>{{t 'article_list'}}</h1>
   
   {{! one line comment }}
   
   {{#each articles}}
    {{~title}}
    <p>{{excerpt body size=120 ellipsis=true}}</p>
   
    {{#with author}}
    written by {{first_name}} {{last_name}}
    from category: {{../category.title}}
    {{#if @../last}}foobar!{{/if}}
    {{/with~}}
   
    {{#if promoted.latest}}Read this one! {{else}} This is ok! {{/if}}
   
    {{#if @last}}<hr>{{/if}}
   {{/each}}
   
   {{#form new_comment}}
    <input type="text" name="body">
   {{/form}}
   

Expected Results

Code is highlighted as seen on https://codemirror.net/mode/handlebars/index.html

Actual Results

Code is not highlighted