Fix ToLinen docstring return description

[mohsinm-dev]

What does this PR do?

Summary

Fixes the incorrect docstring in the ToLinen class.

Changes

• Fixed the "Returns" section in ToLinen docstring
• Changed from "A stateful NNX module that behaves the same as the wrapped Linen module"
• To "A Linen module that behaves the same as the wrapped NNX module"

Issue

• ToLinen: Wraps NNX module → returns Linen module
• ToNNX: Wraps Linen module → returns NNX module

The docstring was incorrectly copied from ToNNX and not updated properly.

Fixes #4803

Checklist

• This PR fixes a minor issue (e.g.: typo or small bug) or improves the docs (you can dismiss the other
  checks if that's the case).
• This change is discussed in a Github issue/
  discussion (please add a
  link).
• The documentation and docstrings adhere to the
  documentation guidelines.
• This change includes necessary high-coverage tests.
  (No quality testing = no merge!)

[google-cla]

Thanks for your pull request! It looks like this may be your first contribution to a Google open source project. Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

View this failed invocation of the CLA check for more information.

For the most up to date status, view the checks section at the bottom of the pull request.

[vfdev-5]

Thanks @mohsinm-dev !