Rust

Minor: reduce unwraps in datetime_expressions.rs #22804

Job	Run time
Check cargo fmt	44s
cargo check	2m 29s
build with wasm-pack	2m 10s
cargo test (macos)	23m 38s
Verify MSRV (Min Supported Rust Version)	7m 41s
Verify Vendored Code	1m 5s
cargo test (win64)	41m 32s
cargo test datafusion-cli (amd64)	3m 43s
cargo examples (amd64)	8m 6s
cargo test (amd64)	9m 6s
check Cargo.toml formatting	1m 29s
clippy	4m 39s
check configs.md is up-to-date	2m 32s
cargo test hash collisions (amd64)	8m 41s
cargo doc	3m 13s
cargo test doc (amd64)	10m 56s
Run sqllogictest with Postgres runner	3m 14s
cargo test pyarrow (amd64)	2m 34s
verify benchmark results (amd64)	10m 1s
	2h 27m 33s

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