Apply nightly clippy fixes (#11508)

# Description

Clippy fixes

# User-Facing Changes
N/A

crates/nu-cmd-extra/src/extra/strings/str_/mod.rs

@@ -1,3 +1 @@
 pub(crate) mod case;
-
-pub use case::*;

crates/nu-command/src/strings/parse.rs

@@ -321,9 +321,7 @@ impl Iterator for ParseStreamer {
                 }
             }
 
-            let Some(v) = self.stream.next() else {
-                return None;
-            };
+            let v = self.stream.next()?;
 
             let Ok(s) = v.as_string() else {
                 return Some(Value::error(

crates/nu-command/src/strings/str_/index_of.rs

@@ -27,9 +27,6 @@ impl CmdArgument for Arguments {
 #[derive(Clone)]
 pub struct SubCommand;
 
-#[derive(Clone)]
-pub struct IndexOfOptionalBounds(i32, i32);
-
 impl Command for SubCommand {
     fn name(&self) -> &str {
         "str index-of"

src/test_bins.rs

@@ -181,7 +181,7 @@ pub fn chop() {
     let stdin = io::stdin();
     let mut stdout = io::stdout();
 
-    for given in stdin.lock().lines().flatten() {
+    for given in stdin.lock().lines().map_while(Result::ok) {
         let chopped = if given.is_empty() {
             &given
         } else {