Fix multiple jspsych instance running issue

[Shaobin-Jiang]

Fixes #3253

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Latest commit: f8ec77af20b563990900c9ab1bcd6004022c3cc7

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
jspsych	Patch

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[jodeleeuw]

Thanks @Shaobin-Jiang !

I'm worried that this might not be sufficient to fix all the issues, in the event that there are other places in the code where a single #jspsych-content div is expected. I'm thinking about adding some tests before merging this.