FIX Support nested redux forms

Description

Allows nested redux-forms to be submitted without propogating the nested submit event up to the parent form.

Add the associated PRs (see issue) to your site
Upload a file to your site
Set up an elemental block that has links (single or multi doesn't matter)
Add a file link
Select "choose existing" and then select the file
Make sure your browser window width is less than 992px wide (the "insert" button when you've selected the file should become "insert file")
Click "insert file" (this should add the file to the upload field and NOT submit the link form)
Save the link (this should not give you a console warning about not returning a promise)

[x] The target branch is correct
- See picking the right version
[x] All commits are relevant to the purpose of the PR (e.g. no debug statements, unrelated refactoring, or arbitrary linting)
- Small amounts of additional linting are usually okay, but if it makes it hard to concentrate on the relevant changes, ask for the unrelated changes to be reverted, and submitted as a separate PR.
[x] The commit messages follow our commit message guidelines
[x] The PR follows our contribution guidelines
[x] Code changes follow our coding conventions
[x] CI is green