Delta: Fix invalid @Returns Javadoc tag in SnapshotDeltaLakeTable

[thswlsqls]

Summary

• The as, icebergCatalog, and deltaLakeConfiguration builder methods appended @Returns this for method chaining to their @param line.
• @Returns is not a valid Javadoc tag, so the return value was never documented.
• Replaced it with a @return this for method chaining line, matching the sibling methods tableProperties, tableProperty, and tableLocation in the same interface (lines 38, 48, 57), which already use @return on its own line.
• File: delta-lake/src/main/java/org/apache/iceberg/delta/SnapshotDeltaLakeTable.java.

Testing done

• Docs/comment-only change, no behavior change — no test added. ./gradlew :iceberg-delta-lake:spotlessCheck passed.

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AI Disclosure

• Model: Claude Opus 4.8
• Platform/Tool: Claude Code