Fix clippy failures with Rust 1.81.0

The recently released Rust 1.81.0 introduced some new on by default
clippy rules and these rules are flagging issues in the rust code in the
library. While we use Rust 1.70 for clippy in CI and these won't cause
failures until we raise our MSRV to >= 1.81.0 these clippy
warnings/failures are still good to fix as the either make the code more
consise and/or efficient. This commit fixes these issues identified by
clippy.

crates/accelerate/src/remove_diagonal_gates_before_measure.rs

@@ -49,7 +49,9 @@ fn run_remove_diagonal_before_measure(dag: &mut DAGCircuit) -> PyResult<()> {
     let mut nodes_to_remove = Vec::new();
     for index in dag.op_nodes(true) {
         let node = &dag.dag[index];
-        let NodeType::Operation(inst) = node else {panic!()};
+        let NodeType::Operation(inst) = node else {
+            panic!()
+        };
 
         if inst.op.name() == "measure" {
             let predecessor = (dag.quantum_predecessors(index))

crates/accelerate/src/results/marginalization.rs

@@ -26,16 +26,11 @@ fn marginalize<T: std::ops::AddAssign + Copy>(
     indices: Option<Vec<usize>>,
 ) -> HashMap<String, T> {
     let mut out_counts: HashMap<String, T> = HashMap::with_capacity(counts.len());
-    let clbit_size = counts
-        .keys()
-        .next()
-        .unwrap()
-        .replace(|c| c == '_' || c == ' ', "")
-        .len();
+    let clbit_size = counts.keys().next().unwrap().replace(['_', ' '], "").len();
     let all_indices: Vec<usize> = (0..clbit_size).collect();
     counts
         .iter()
-        .map(|(k, v)| (k.replace(|c| c == '_' || c == ' ', ""), *v))
+        .map(|(k, v)| (k.replace(['_', ' '], ""), *v))
         .for_each(|(k, v)| match &indices {
             Some(indices) => {
                 if all_indices == *indices {

crates/circuit/src/operations.rs

@@ -2225,10 +2225,7 @@ impl Operation for PyGate {
     fn standard_gate(&self) -> Option<StandardGate> {
         Python::with_gil(|py| -> Option<StandardGate> {
             match self.gate.getattr(py, intern!(py, "_standard_gate")) {
-                Ok(stdgate) => match stdgate.extract(py) {
-                    Ok(out_gate) => out_gate,
-                    Err(_) => None,
-                },
+                Ok(stdgate) => stdgate.extract(py).unwrap_or_default(),
                 Err(_) => None,
             }
         })