Fix minecraft AI for good link

[maureensturgeon]

Issue: https://codedotorg.atlassian.net/browse/LP-1706
Previously link was going to https://code.org/www.education.minecraft.net/hour-of-code-2019 which was causing a 404, this fix updates link to https://education.minecraft.net/hour-of-code-2019. Tested locally.

Links

https://codedotorg.atlassian.net/browse/LP-1706

• spec
• jira

Testing story

Tested locally at http://localhost.code.org:3000/minecraft

Reviewer Checklist:

• Tests provide adequate coverage
• Privacy and Security impacts have been assessed
• Code is well-commented
• New features are translatable or updates will not break translations
• Relevant documentation has been added or updated
• User impact is well-understood and desirable
• Pull Request is labeled appropriately
• Follow-up work items (including potential tech debt) are tracked and linked