### Summary Pasting code block copied from Comment Cannot be Undone ### Steps to reproduce * Create a new issue in a test project * Add the following ruby code block as a comment ```ruby x = 1 + 1 y = x + 1 ``` * Select the above Ruby code block in your latest comment and copy and paste into a new comment * The response should be pasted with `ruby` code block in tact * Attempt to undo your action with `Cmd` + `z` ### What is the current *bug* behavior? The paste of the code block isn't undone, as expected ### What is the expected *correct* behavior? The paste of the code block should be undone ### Relevant logs and/or screenshots N/A ### Output of checks gitlab-ce~3293941 #### Results of GitLab environment info gitlab-ce~3293941