[Docs] Update Examples to Replace Hadoop Catalog with JDBC Catalog

[kevinjqliu]

Feature Request / Improvement

The current documentation includes examples of using the Hadoop catalog with Iceberg, such as:

• https://iceberg.apache.org/spark-quickstart/#adding-a-catalog
• https://iceberg.apache.org/docs/nightly/spark-getting-started/#adding-catalogs

Since we discourage the use of Hadoop catalogs in production environments, it would be beneficial to replace these examples with ones that use the JDBC catalog. The JDBC catalog, when configured with a local SQLite database file, is just as convenient as the Hadoop catalog for these purposes.

I’m opening this issue to discuss whether this is a direction we want to pursue.

Query engine

None

Willingness to contribute

• I can contribute this improvement/feature independently
• I would be willing to contribute this improvement/feature with guidance from the Iceberg community
• I cannot contribute this improvement/feature at this time