Minor: Improve `DataFusionError` documentation #21875

Job	Run time
cargo check	3m 45s
build with wasm-pack	1m 55s
cargo test (mac)	18m 36s
cargo test (win64)	38m 54s
Check cargo fmt	38s
Verify MSRV	6m 23s
Verify Vendored Code	45s
cargo test (amd64)	8m 44s
clippy	4m 2s
cargo doc	3m 4s
cargo test hash collisions (amd64)	8m 25s
cargo test datafusion-cli (amd64)	2m 58s
cargo examples (amd64)	6m 43s
cargo test doc (amd64)	9m 19s
Run sqllogictest with Postgres runner	3m 6s
cargo test pyarrow (amd64)	2m 16s
verify benchmark results (amd64)	9m 47s
check Cargo.toml formatting	1m 22s
check configs.md is up-to-date	2m 8s
	2h 12m 50s

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