docs(deployment): Describe what the shipped Kafka ingester configs demonstrate

[ysh-bot]

Which problem is this PR solving?

#1149 merged before its last review-round commit reached the branch, so four prose corrections from that round are missing on main.

Description of the changes

• The Delivery Guarantees and Kafka pages no longer call the shipped ingester files config-kafka-ingester-sync.yaml and config-kafka-ingester-dead-letter.yaml "the complete ingester configuration". They say the files demonstrate the offset coupling but set queue.batch.min_size: 0, omit block_on_overflow, and (for the dead-letter one) end in an otlphttp sink, so a reader copying them knows what differs from the recommended shape.
• The sentence that the retry is safe because span writes are idempotent moves to the retry_on_failure bullet it justifies.
• The translog durability sentence is made grammatical.
• The connector's log line is described as one warning per distinct trace id and span id pair, as the code does.

How was this change tested?

npm run check:format and check:spelling pass; the content is the commit reviewed on #1149.