Update "content editor" to "rich text editor" in docs
What does this MR do and why?
Update "content editor" to "rich text editor" in docs. Related comment: !120850 (comment 1427557955)
Related issue: #409976 (closed), #398152 (closed)
Changelog: changed
MR acceptance checklist
This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.
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I have evaluated the MR acceptance checklist for this MR. 
Edited  by Himanshu Kapoor