fix(rust): Fix ser/de PlSmallStr error

[kgv]

0.42.0 - ser/de - OK
0.43.1 - ser/de - Err: SpannedError { code: ExpectedMapColon, position: Position { line: 1, col: 19 } }

PlSmallStr is tuple struct, but deserialize doesn't expect it
serde(transparent) fix this

let data_frame = df! {
    "STRING" => &["1", "2"],
}
.unwrap();
let string = ron::ser::to_string(&data_frame).unwrap();
println!("string: {string}");
// 0.42.0: string: (columns:[{"name":"STRING","datatype":String,"bit_settings":"","values":[Some("1"),Some("2")]}])
// 0.43.1: string: (columns:[{"name":("STRING"),"datatype":String,"bit_settings":"","values":[Some("1"),Some("2")]}])
let data_frame = ron::from_str::<DataFrame>(&string).unwrap();
println!("data_frame: {data_frame}");

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 79.76%. Comparing base (a2d00f1) to head (411e0f6).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #19060      +/-   ##
==========================================
- Coverage   79.77%   79.76%   -0.01%     
==========================================
  Files        1531     1531              
  Lines      208487   208487              
  Branches     2913     2913              
==========================================
- Hits       166320   166304      -16     
- Misses      41616    41632      +16     
  Partials      551      551              

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