🐛 Missing entities generate a sentry error

[MatMoore]

Describe the bug.

When Find MoJ data returns a 404, we still get an error in sentry.

However, it is normal for the service to return 404 when a catalogue entry does not exist. This might happen because a dataset has been removed or renamed (causing the URN to change), but somebody still has an old url bookmarked.

These kinds of errors clutter up sentry and obscure actual issues requiring attention

Example:
https://ministryofjustice.sentry.io/issues/6267209271/?environment=prod&query=is%3Aunresolved%20issue.priority%3A%5Bhigh%2C%20medium%5D&referrer=issue-stream&statsPeriod=30d&stream_index=2

To Reproduce

1. Open a dataset in Find MoJ data.
2. Change the urn to a urn that doesn't exist

Expected Behaviour

• Find MoJ data displays the 404 page
• No sentry errors

Additional context

No response