Added introspection fragment matcher to Epic Boards

What does this MR do?

This MR adds an IntrospectionFragmentMatcher to Epic Boards to fix this console warning:

Does this MR meet the acceptance criteria?

Conformity

• 📋 Does this MR need a changelog?
  • I have included a changelog entry.
  • I have not included a changelog entry because this MR fixes only developer-facing error.
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content