Fix clippy with Rust 1.66.0 (#762)

The recent release of Rust 1.66.0 [1] added new on by default clippy rules
which are causing failures when we run the clippy CI job with the new
rust version. This commit updates the code to fix the issues that clippy
has identified which will unblock CI.

[1] https://blog.rust-lang.org/2022/12/15/Rust-1.66.0.html

src/digraph.rs

@@ -2688,14 +2688,14 @@ impl PyDiGraph {
     }
 
     fn __getitem__(&self, idx: usize) -> PyResult<&PyObject> {
-        match self.graph.node_weight(NodeIndex::new(idx as usize)) {
+        match self.graph.node_weight(NodeIndex::new(idx)) {
             Some(data) => Ok(data),
             None => Err(PyIndexError::new_err("No node found for index")),
         }
     }
 
     fn __setitem__(&mut self, idx: usize, value: PyObject) -> PyResult<()> {
-        let data = match self.graph.node_weight_mut(NodeIndex::new(idx as usize)) {
+        let data = match self.graph.node_weight_mut(NodeIndex::new(idx)) {
             Some(node_data) => node_data,
             None => return Err(PyIndexError::new_err("No node found for index")),
         };
@@ -2704,7 +2704,7 @@ impl PyDiGraph {
     }
 
     fn __delitem__(&mut self, idx: usize) -> PyResult<()> {
-        match self.graph.remove_node(NodeIndex::new(idx as usize)) {
+        match self.graph.remove_node(NodeIndex::new(idx)) {
             Some(_) => Ok(()),
             None => Err(PyIndexError::new_err("No node found for index")),
         }

src/graph.rs

@@ -1746,7 +1746,7 @@ impl PyGraph {
     }
 
     fn __delitem__(&mut self, idx: usize) -> PyResult<()> {
-        match self.graph.remove_node(NodeIndex::new(idx as usize)) {
+        match self.graph.remove_node(NodeIndex::new(idx)) {
             Some(_) => Ok(()),
             None => Err(PyIndexError::new_err("No node found for index")),
         }