[docs] Improve Incremental Snapshot Reading formatting and references

[nhuantho]

What is the purpose of this pull request?

While reading the Flink PostgreSQL CDC documentation, I found that the reference link for scan.incremental.snapshot.enabled in the Connector Options section is incorrect. It points to an outdated anchor.

Brief change log

• Clarified the three key advantages of incremental snapshot reading by adding HTML line breaks (<br/>) for improved readability.
• Fixed the internal documentation link to point to the correct Incremental Snapshot Reading section (#incremental-snapshot-reading-experimental) instead of the outdated experimental anchor (#incremental-snapshot-reading).

---

Was generative AI tooling used to co-author this PR?

• Yes (please specify the tool below)

[nhuantho]

@loserwang1024, could you please review this for me?

[yuxiqian]

Thank you for your nice patch! Could you please update the docs/content.zh/docs/connectors/flink-sources/postgres-cdc.md, too?

[nhuantho]

@yuxiqian thank you for your review, I updated docs/content.zh/docs/connectors/flink-sources/postgres-cdc.md.

[yuxiqian]

LGTM, thank you for the contribution.