Remove fallback logic

What does this MR do?

Part of #321678 (closed)

This change was suggested in a review comment.

Remove fallback logic for license, from and to in HistoricalData#max_historical_user_count by moving it outside of this method. The scope of this refactor got a bit bigger than expected with the footprint of that method.

HistoricalData#in_license_term was moved to License (License#historical_data) as it seemed fitting with the removal of its fallback values.

This shouldn't need a changelog since it falls under:

Any developer-facing change (e.g., refactoring, technical debt remediation, test suite changes) should not have a changelog entry. Example: “Reduce database records created during Cycle Analytics model spec.”

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

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• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team