Unescape HTML characters in Wiki title

The special characters of a wiki title are now escaped correctly.

app/models/wiki_page.rb

@@ -84,7 +84,7 @@ class WikiPage
   # The formatted title of this page.
   def title
     if @attributes[:title]
-      self.class.unhyphenize(@attributes[:title])
+      CGI.unescape_html(self.class.unhyphenize(@attributes[:title]))
     else
       ""
     end

changelogs/unreleased/35686-unescape-wiki-title.yml

+---
+title: Unescape HTML characters in Wiki title
+merge_request: 13942
+author: Jacopo Beschi @jacopo-beschi
+type: fixed

spec/models/wiki_page_spec.rb

@@ -281,6 +281,12 @@ describe WikiPage do
       @page.title = "Import-existing-repositories-into-GitLab"
       expect(@page.title).to eq("Import existing repositories into GitLab")
     end
+
+    it 'unescapes html' do
+      @page.title = 'foo & bar'
+
+      expect(@page.title).to eq('foo & bar')
+    end
   end
 
   describe '#directory' do