Fixes #12482 by pointing help links for ndjson to a non-spam source (take 2) (#12509)

<!--
if this PR closes one or more issues, you can automatically link the PR
with
them by using one of the [*linking
keywords*](https://docs.github.com/en/issues/tracking-your-work-with-issues/linking-a-pull-request-to-an-issue#linking-a-pull-request-to-an-issue-using-a-keyword),
e.g.
- this PR should close #xxxx
- fixes #xxxx

you can also mention related issues, PRs or discussions!
-->

* Fixes #12482
* Initial PR failed due to CI issues at the time. Subsequent rebase
failed, so creating new PR.

# Description
<!--
Thank you for improving Nushell. Please, check our [contributing
guide](../CONTRIBUTING.md) and talk to the core team before making major
changes.

Description of your pull request goes here. **Provide examples and/or
screenshots** if your changes affect the user experience.
-->

Use https://github.com/ndjson/ndjson-spec for help links instead of
former spam site

# User-Facing Changes
<!-- List of all changes that impact the user experience here. This
helps us keep track of breaking changes. -->

Link changed for `help to ndjson` and `help from ndjson`.

# 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` to
check that you're using the standard code style
- `cargo test --workspace` to check that all tests pass (on Windows make
sure to [enable developer
mode](https://learn.microsoft.com/en-us/windows/apps/get-started/developer-mode-features-and-debugging))
- `cargo run -- -c "use std testing; testing run-tests --path
crates/nu-std"` to run the tests for the standard library

> **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
> ```
-->

- 🟢 `toolkit fmt`
- 🟢 `toolkit clippy`
- 🟢 `toolkit test`
- 🟢 `toolkit test stdlib`


# 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-std/std/formats.nu

@@ -9,7 +9,7 @@
 # These functions help `open` the files with unsupported extensions such as ndjson.
 #
 
-# Convert from [NDJSON](http://ndjson.org/) to structured data.
+# Convert from [NDJSON](https://github.com/ndjson/ndjson-spec) to structured data.
 export def "from ndjson" []: string -> any {
     from json --objects
 }
@@ -19,7 +19,7 @@ export def "from jsonl" []: string -> any {
     from json --objects
 }
 
-# Convert structured data to [NDJSON](http://ndjson.org/).
+# Convert structured data to [NDJSON](https://github.com/ndjson/ndjson-spec).
 export def "to ndjson" []: any -> string {
     each { to json --raw } | to text
 }