Update multiversx-ecosystem.md

[mdqst]

Description of the pull request (what is new / what has changed)

The use of "that" here is incorrect; "whether" is the appropriate word in this context.

Did you test the changes locally ?

• [x] yes
• [ ] no

Which category (categories) does this pull request belong to?

• [ ] document new feature
• [ ] update documentation that is not relevant anymore
• [ ] add examples or more information about a component
• [x] fix grammar issues
• [ ] other