Merge branch 'redcloth-4-3-2-cve-2012-6684' into 'master'

Update RedCloth to 4.3.2 for CVE-2012-6684

## What does this MR do?

To fix XSS (CVE-2012-6684), upgrade RedCloth to 4.3.2.

## Are there points in the code the reviewer needs to double check?

No.

## Why was this MR needed?

Security vulnerability in RedCloth (CVE-2012-6684) should be fixed to provide GitLab as a secure software.

## What are the relevant issue numbers?

Closes #19169

cf. !2037, !2071

## Does this MR meet the acceptance criteria?

- [x] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- [n/a] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- [n/a] API support added
- Tests
  - [n/a] Added for this feature/bug
  - [x] All builds are passing
- [x] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [x] Branch has no merge conflicts with `master` (if you do - rebase it please)
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

See merge request !4929
(cherry picked from commit 95336861)

CHANGELOG

 Please view this file on the master branch, on stable branches it's out of date.
 
 v 8.9.5
+  - Update RedCloth to 4.3.2 for CVE-2012-6684. !4929 (Takuya Noguchi)
   - Improve the request / withdraw access button. !4860
 
 v 8.9.4

Gemfile

@@ -106,7 +106,7 @@ gem 'html-pipeline', '~> 1.11.0'
 gem 'task_list',     '~> 1.0.2', require: 'task_list/railtie'
 gem 'github-markup', '~> 1.3.1'
 gem 'redcarpet',     '~> 3.3.3'
-gem 'RedCloth',      '~> 4.2.9'
+gem 'RedCloth',      '~> 4.3.2'
 gem 'rdoc',          '~>3.6'
 gem 'org-ruby',      '~> 0.9.12'
 gem 'creole',        '~> 0.5.0'

Gemfile.lock

 GEM
   remote: https://rubygems.org/
   specs:
-    RedCloth (4.2.9)
+    RedCloth (4.3.2)
     ace-rails-ap (4.0.2)
     actionmailer (4.2.6)
       actionpack (= 4.2.6)
@@ -813,7 +813,7 @@ PLATFORMS
   ruby
 
 DEPENDENCIES
-  RedCloth (~> 4.2.9)
+  RedCloth (~> 4.3.2)
   ace-rails-ap (~> 4.0.2)
   activerecord-session_store (~> 1.0.0)
   acts-as-taggable-on (~> 3.4)