Error message needs line breaks

[rmoff]

c.f. #7204

This error message:

Schema for message keys on topic FOO2 does not exist in the Schema Registry.Subject: FOO2-key
Possible causes include:
- The topic itself does not exist       -> Use SHOW TOPICS; to check
- Messages on the topic are not serialized using a format Schema Registry supports      -> Use PRINT 'FOO2' FROM BEGINNING; to verify
- Messages on the topic have not been serialized using a Confluent Schema Registry supported serializer -> See https://docs.confluent.io/current/schema-registry/docs/serializer-formatter.html
- The schema is registered on a different instance of the Schema Registry       -> Use the REST API to list available subjects  https://docs.confluent.io/current/schema-registry/docs/api.html#get--subjects
- You do not have permissions to access the Schema Registry.Subject: FOO2-key   -> See https://docs.confluent.io/current/schema-registry/docs/security.html

Should be formatted for better readability as:

Schema for message keys on topic FOO2 does not exist in the Schema Registry.Subject: FOO2-key
Possible causes include:
- The topic itself does not exist
  -> Use SHOW TOPICS; to check
- Messages on the topic are not serialized using a format Schema Registry supports
  -> Use PRINT 'FOO2' FROM BEGINNING; to verify
- Messages on the topic have not been serialized using a Confluent Schema Registry supported serializer
 -> See https://docs.confluent.io/current/schema-registry/docs/serializer-formatter.html
- The schema is registered on a different instance of the Schema Registry
  -> Use the REST API to list available subjects  https://docs.confluent.io/current/schema-registry/docs/api.html#get--subjects
- You do not have permissions to access the Schema Registry.Subject: FOO2-key
  -> See https://docs.confluent.io/current/schema-registry/docs/security.html