Fix fetch/post not erroring on 4xx and 5xx statuses (#7213)

# Description

Closes #6803.

You can look at the code and see this was always supposed to work this
way, but was broken due to 1 line (per file).

# User-Facing Changes

See above.

# 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

# 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/network/fetch.rs

@@ -450,7 +450,8 @@ fn helper(
         }
     }
 
-    match request.send() {
+    // Explicitly turn 4xx and 5xx statuses into errors.
+    match request.send().and_then(|r| r.error_for_status()) {
         Ok(resp) => match resp.headers().get("content-type") {
             Some(content_type) => {
                 let content_type = content_type.to_str().map_err(|e| {

crates/nu-command/src/network/post.rs

@@ -304,7 +304,8 @@ fn helper(
         }
     }
 
-    match request.send() {
+    // Explicitly turn 4xx and 5xx statuses into errors.
+    match request.send().and_then(|r| r.error_for_status()) {
         Ok(resp) => match resp.headers().get("content-type") {
             Some(content_type) => {
                 let content_type = content_type.to_str().map_err(|e| {