Two typos in smallrye-kafka connector tables

**Describe the bug**

The descriptions of the attributes

- **topics** in Table 1 (_Incoming Attributes of the 'smallrye-kafka' connector_),
- **propagate-headers** in Table 2 (_Outgoing Attributes of the 'smallrye-kafka' connector_)

start with _A comma-separating list_, but should start with _A comma-separated list_.

**Which pages**

https://quarkus.io/guides/kafka
