Broadcast messages are not rendered in preview

Summary

Broadcast messages are not rendered in the preview after the upgrade to GitLab 15.8.0.

Steps to reproduce

• upgrade your GitLab instance to 15.8.0
• go to Menu > Admin > Messages and create some new message with markdown and/or HTML tags, for instance: **This is** a test message <br>please ignore

What is the current bug behavior?

The message is shown as is in the preview: markdown and HTML is rendered.

What is the expected correct behavior?

Before the upgrade, markdown and HTML syntax was properly rendered in the preview.

Note that when you save the message by clicking Add broadcast message, it will be shown correctly in GitLab.

Relevant logs and/or screenshots

Output of checks

Results of GitLab environment info

Expand for output related to GitLab environment info

System information
System:   Debian 10
Proxy:    no
Current User: git
Using RVM:  no
Ruby Version: 2.7.7p221
Gem Version:  3.1.6
Bundler Version:2.3.15
Rake Version: 13.0.6
Redis Version:  6.2.8
Sidekiq Version:6.5.7
Go Version: unknown

GitLab information
Version:  15.8.0-ee
Revision: 1d89c23c9f9
Directory:  /opt/gitlab/embedded/service/gitlab-rails
DB Adapter: PostgreSQL
DB Version: 12.12
URL:    https://gitlabhost.tld
HTTP Clone URL: https://gitlabhost.tld/some-group/some-project.git
SSH Clone URL:  git@gitlabhost.tld:some-group/some-project.git
Elasticsearch:  no
Geo:    yes
Geo node: Undefined
Using LDAP: no
Using Omniauth: yes
Omniauth Providers:

GitLab Shell
Version:  14.15.0
Repository storages:
- default:  unix:/var/opt/gitlab/gitaly/gitaly.socket
GitLab Shell path:    /opt/gitlab/embedded/service/gitlab-shell

Possible fixesil