Remove unnecessary conversion name.to_string()

Response to reviewer comment https://github.com/Qiskit/qiskit/pull/12087/files#r1586949717

crates/qasm3/src/build.rs

@@ -231,12 +231,11 @@ impl BuilderState {
     // Gates mapped via CustomGates will not raise an exception.
     fn map_gate_ids(&mut self, _py: Python, ast_symbols: &SymbolTable) -> PyResult<()> {
         for (name, name_id, defined_num_params, defined_num_qubits) in ast_symbols.gates().iter() {
-            let name = name.to_string();
-            if name == "U" {
+            if *name == "U" {
                 // The sole built in gate. `gphase` is treated specially.
                 continue;
             }
-            let pygate = self.pygates.get(&name).ok_or_else(|| {
+            let pygate = self.pygates.get(*name).ok_or_else(|| {
                 QASM3ImporterError::new_err(format!("can't handle non-built-in gate: '{}'", name))
             })?;
             if pygate.num_params() != *defined_num_params {