Update rstest requirement from 0.19.0 to 0.20.0 #1375

Job	Run time
cargo test (macos)	8m 52s
cargo check	3m 42s
build with wasm-pack	2m 10s
cargo test (win64)	32m 27s
Check cargo fmt	42s
cargo test (macos-aarch64)	10m 4s
Verify MSRV (Min Supported Rust Version)	6m 29s
Verify Vendored Code	45s
cargo examples (amd64)	11m 44s
cargo doc	3m 42s
cargo test datafusion-cli (amd64)	3m 39s
cargo test (amd64)	9m 14s
cargo test doc (amd64)	12m 3s
Run sqllogictest with Postgres runner	3m 14s
cargo test pyarrow (amd64)	2m 35s
clippy	5m 5s
check Cargo.toml formatting	2m 42s
verify benchmark results (amd64)	10m 39s
check configs.md is up-to-date	2m 30s
cargo test hash collisions (amd64)	9m 13s
	2h 21m 31s

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