Rust

Remove redundant type constraints from ScalarUDF from #391

Job	Run time
cargo test (win64)	4m 31s
Check License Header	2m 12s
cargo check	1m 15s
Check cargo fmt	47s
build with wasm-pack	1m 53s
cargo test (macos)	2m 18s
cargo test (macos-aarch64)	2m 38s
Verify MSRV (Min Supported Rust Version)	5m 48s
Verify Vendored Code	50s
cargo test datafusion-cli (amd64)	0s
cargo test (amd64)	0s
cargo examples (amd64)	0s
Run sqllogictest with Postgres runner	0s
check Cargo.toml formatting	0s
cargo doc	0s
verify benchmark results (amd64)	0s
clippy	0s
cargo test hash collisions (amd64)	0s
cargo test pyarrow (amd64)	0s
check configs.md and ***_functions.md is up-to-date	0s
cargo test doc (amd64)	0s
	22m 12s

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