fix: allow to see multiple xblock mindmap in lms

[johnvente]

Description
When we create more than one XBlock per unit in the LMS, it breaks due to a draggable plugin from jsmind that was initialized previously, which is weird because each XBlock in the LMS is an iframe. This fix allows us to create any number of XBlocks without that issue

BEFORE	NOW

How to test

1. Once you have the XBlock in your environment, go to Studio > create a unit > create some XBlock-type mind maps.
2. Publish the changes.
3. Go to the LMS to see the unit.

Merge checklist:
Check off if complete or not applicable:

• Version bumped
• Documentation updated (not only docstrings)
• Fixup commits are squashed away
• Unit tests added/updated
• Manual testing instructions provided
• Noted any: Concerns, dependencies, migration issues, deadlines, tickets
• Changelog record added

[mariajgrimaldi]

The error was fixed! Thanks

[BryanttV]

@johnvente, when I add more than one block to the unit it does not allow me to display the instructions for use, it closes by itself.

[johnvente]

@johnvente, when I add more than one block to the unit it does not allow me to display the instructions for use, it closes by itself.

@BryanttV Nice catch! I've done the fix for that

[BryanttV]

@johnvente, good! It no longer closes by itself, however, when I open/close one block's instructions, the other blocks do the same.

[johnvente]

@johnvente, good! It no longer closes by itself, however, when I open/close one block's instructions, the other blocks do the same.

@BryanttV too odd, fixed it! 🚀

[BryanttV]

Perfect! 💯 , LGTM