Attachment name remained after attachment deletion

[biallenchanuow]

Environment
Jupyter Notebook version: 6.3.0
Conda version: 4.10.1
Python version: 3.7.10
Platform: Mac OS version 10.15.3
Browser Version: Google Chrome - Version 90.0.4430.212 (Official Build) (x86_64)

Description
1.Created a cell and changed its type to "Markdown"
2.Inserted an image as an attachment
3.Clicked "Edit Attachment" button on the "Attachment" Toolbar
4.Clicked the delete icon (the red bin) and clicked "Apply"
5.A broken image icon appeared, and after clicking on it, the attachment name re-appeared
6.Clicked "Edit Attachments" again
7.The popup window indicated that "There are no attachments for this cell.", but after clicking "Apply", the attachment name remained.

Failure.7_attachment_name_remained_after_deletion.1080.mov

[jtpio]

Bumping as we will likely need jupyterlab/jupyterlab#14663 to be available in JupyterLab first.