Markdown is saved as Confluence Wiki on the preview regardless of language mode

Issue Summary

Adding Markdown via the Markup tool into Confluence Page will render in Confluence Wiki view instead of Markdown

Steps to Reproduce

1. Create a new page (any type, tested on Blank)
2. Click on Insert More Content drop down menu
3. Switch to markdown mode and Insert a Markdown code
   
   ^ The preview renders correctly
4. Insert to page

Expected Results

Codes are rendered in Markdown

Actual Results

Codes are rendered in Confluence Wiki format instead of Markdown.

Error appears on the Console:

[Error] SyntaxError: JSON Parse error: Unexpected identifier "MARKDOWN"
	parse (atlassian-editor-plugins.d029127af5fa4a104e5c-v38.js:1:176019)
	Mn (atlassian-editor-plugins.d029127af5fa4a104e5c-v38.js:1:176019)
	(anonymous function) (atlassian-editor-plugins.d029127af5fa4a104e5c-v38.js:1:179932)
	execCommand (vendors~atlassian-editor.cf420a9674f38f58ca00-v38.js:1:27887)
	b (batch.js:508:511)
	(anonymous function) (atlassian-editor-plugins.d029127af5fa4a104e5c-v38.js:1:160984)
	(anonymous function) (atlassian-editor-plugins.d029127af5fa4a104e5c-v38.js:1:161102)
	dispatch (jquery-min.js:1:32141)
	a (jquery-min.js:1:27832)

Notes

There is another bug reported which might be related: CONFCLOUD-65841: Markup macros prompt no longer popup the second time

Workaround

• Please use Confluence Wiki as there is no workaround to use Markdown at the moment.
• Use Markdown to Wiki Converter tool: http://chunpu.github.io/markdown2confluence/browser/
• Create pages using the new editor instead as the new editor is not affected by this bug