[Forward port to 11.0] bold+italic combination in CKEditor does not correctly render in the CMS

Steps to reproduce:-->
1.Open a document in edit mode.
2.Select a text in Ckeditor
3.Click on "Bold" in Ckeditor toolbar
4.Now click on Italic" in Ckeditor toolbar.
5.Notice there is no effect of italic on select text.

Note:-->Same can be noticed for Bold if Italic is selected first & then Bold.

Expected:-->Combination of Bold+Italic should work.