When running external command, expand tilde when pass back-quoted word (#8561)

# Description

Fixes: #8542

# User-Facing Changes

## Previous
```
❯ cat `~/TE ST/bug`
cat: ~/TE ST/bug: No such file or directory
```

## After
```
❯ cat `~/TE ST/bug`
a
```

This should be ok because We treat back-quoted strings as bare words

# Tests + Formatting

Don't forget to add tests that cover your changes.

Make sure you've run and fixed any issues with these commands:

- `cargo fmt --all -- --check` to check standard code formatting (`cargo
fmt --all` applies these changes)
- `cargo clippy --workspace -- -D warnings -D clippy::unwrap_used -A
clippy::needless_collect` to check that you're using the standard code
style
- `cargo test --workspace` to check that all tests pass

> **Note**
> from `nushell` you can also use the `toolkit` as follows
> ```bash
> use toolkit.nu # or use an `env_change` hook to activate it
automatically
> toolkit check pr
> ```

# After Submitting

If your PR had any user-facing changes, update [the
documentation](https://github.com/nushell/nushell.github.io) after the
PR is merged, if necessary. This will help us keep the docs up to date.

crates/nu-command/src/system/run_external.rs

@@ -778,7 +778,8 @@ fn trim_enclosing_quotes(input: &str) -> (String, bool, bool) {
     match (chars.next(), chars.next_back()) {
         (Some('"'), Some('"')) => (chars.collect(), false, true),
         (Some('\''), Some('\'')) => (chars.collect(), false, true),
-        (Some('`'), Some('`')) => (chars.collect(), true, true),
+        // We treat back-quoted strings as bare words, so there's no need to keep them as raw strings
+        (Some('`'), Some('`')) => (chars.collect(), true, false),
         _ => (input.to_string(), true, false),
     }
 }

crates/nu-command/tests/commands/run_external.rs

@@ -213,6 +213,17 @@ fn external_command_not_expand_tilde_with_quotes() {
     )
 }
 
+#[test]
+fn external_command_expand_tilde_with_back_quotes() {
+    Playground::setup(
+        "external command not expand tilde with quotes",
+        |dirs, _| {
+            let actual = nu!(cwd: dirs.test(), pipeline(r#"nu --testbin nonu `~`"#));
+            assert!(!actual.out.contains("~"));
+        },
+    )
+}
+
 #[test]
 fn external_command_receives_raw_binary_data() {
     Playground::setup("external command receives raw binary data", |dirs, _| {