Minor: Remove memory reservation in `JoinLeftData` used in HashJoin #35869

Job	Run time
Check License Header	2m 15s
cargo check	8m 20s
build with wasm-pack	3m 6s
cargo test (macos)	18m 16s
cargo test (win64)	1h 13m 25s
Check cargo fmt	41s
cargo test (macos-aarch64)	15m 59s
Verify MSRV (Min Supported Rust Version)	8m 58s
Verify Vendored Code	50s
cargo examples (amd64)	14m 21s
cargo test (amd64)	12m 9s
cargo doc	4m 31s
cargo test datafusion-cli (amd64)	4m 48s
cargo test doc (amd64)	17m 32s
Run sqllogictest with Postgres runner	3m 58s
cargo test pyarrow (amd64)	3m 1s
verify benchmark results (amd64)	14m 24s
check Cargo.toml formatting	3m 0s
clippy	6m 56s
check configs.md and ***_functions.md is up-to-date	3m 45s
cargo test hash collisions (amd64)	28m 57s
	4h 9m 12s

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