Reduce default number of partitions from 50 to 1

https://github.com/folio-org/folio-kafka-wrapper/blob/v2.7.0/src/main/java/org/folio/kafka/services/KafkaTopic.java#L21-L26

sets the default number of partitions for a topic to 50. No implementer runs 50 instances of a consuming module.

If the administrator doesn't configure the partitions it is very likely a small system where only a single partition is needed.

On bigger systems the administrator doesn't rely on modules to automatically create the partitions but makes use of Kafka admin APIs to create them.

Having too many partitions can be expensive, for details see https://github.com/folio-org/rfcs/pull/6/files

Therefore a default of 1 partition should be the default. Modules can overwrite it if needed.