fix: editor flicker after creating xblock

[rpenido]

Description

This PR fixes the flicker bug described here: #1528 (comment)

Flickering.Editor.mov

Additional Information

The data object is being mutated with the same value, causing the components to re-render.

Note: There is a racing condition involved, so the flicker doesn't happen consistently.

Testing instructions

1. Try to add a new component using the sidebar and check if the flicker stopped happening.

[openedx-webhooks]

Thanks for the pull request, @rpenido!

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[ChrisChV]

@rpenido Looks good 👍

• I tested this: I followed the testing instructions. I verified that the bug does not occur.
• I read through the code and considered the security, stability and performance implications of the changes.
• Includes tests for bugfixes and/or features added.