Minor: use `ready!` macro to simplify `FilterExec` #29858

Job	Run time
cargo check	3m 32s
Check cargo fmt	39s
build with wasm-pack	2m 17s
cargo test (macos)	9m 52s
cargo test (macos-aarch64)	12m 52s
Verify Vendored Code	56s
cargo test (win64)	40m 46s
Verify MSRV (Min Supported Rust Version)	6m 28s
cargo test datafusion-cli (amd64)	3m 49s
cargo examples (amd64)	12m 29s
cargo test (amd64)	9m 30s
check Cargo.toml formatting	2m 50s
clippy	5m 1s
check configs.md is up-to-date	2m 38s
cargo test hash collisions (amd64)	8m 59s
cargo doc	3m 28s
cargo test doc (amd64)	13m 51s
Run sqllogictest with Postgres runner	3m 13s
cargo test pyarrow (amd64)	2m 59s
verify benchmark results (amd64)	11m 8s
	2h 37m 17s

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