Fix CSS so TinyMCE sslink popup windows show over fullscreen

[lianna-blanca]

Description

When using TinyMCE in CMS 5.2, the editor's full screen mode hides the pop-up windows which allow users to configure links. This applies to all types of links (internal, external, file, anchor, email, phone).

This appears to be due to the TinyMCE fullscreen mode having a z-index of 1200, whereas the popup windows are at 1050. When I manually change this in chrome dev tools, the popups appear over the full screen as they should.

Manual testing steps

1. Go to any TinyMCE editor field which has buttons for full screen and for SSLink
2. Open full screen mode
3. Select some text and press the SSLink button, and select any option from the dropdown field
4. Observe that no popup appears
5. Close full screen mode; observe that the popup for editing that link type is now visible.

Issues

• TinyMCE sslink plugin popup windows are hidden in full screen mode #1815

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