Remove unused SmallCString implementation (#550)

Originally copied from
https://github.com/rusqlite/rusqlite/blob/master/src/util/small_cstr.rs
but not actually used.

We can always bring it back.

Author: mlafeldt

Cargo.lock

@@ -52,7 +52,6 @@ rand = "0.9.0"
 rust_decimal = "1.14"
 serde = "1.0"
 serde_json = "1.0"
-smallvec = "1.6.1"
 strum = "0.27"
 syn = "2.0.15"
 tar = "0.4.38"

Cargo.toml

@@ -52,7 +52,6 @@ polars-arrow = { workspace = true, optional = true }
 r2d2 = { workspace = true, optional = true }
 rust_decimal = { workspace = true }
 serde_json = { workspace = true, optional = true }
-smallvec = { workspace = true }
 strum = { workspace = true, features = ["derive"] }
 url = { workspace = true, optional = true }
 uuid = { workspace = true, optional = true }

crates/duckdb/Cargo.toml

@@ -134,8 +134,6 @@ pub mod vscalar;
 #[cfg(test)]
 mod test_all_types;
 
-pub(crate) mod util;
-
 // Number of cached prepared statements we'll hold on to.
 const STATEMENT_CACHE_DEFAULT_CAPACITY: usize = 16;