Fix grammar in PreTrainedConfig description
Author: samyuktahegde
Pull request: yes

<!-- ci-dashboard-badge:start -->
[![CI](https://transformers-ci.lor-e.huggingface.cool/badge/pr?pr=47098)](https://transformers-ci.lor-e.huggingface.cool/d/pytest-observability-by-pr/pytest-observability-branch?var-pr=47098)
<!-- ci-dashboard-badge:end -->

# What does this PR do?

This PR fixes a grammatical error in the `PreTrainedConfig` description in the Quickstart documentation.

Specifically, it changes:

- `a models attributes`
- to `a model's attributes`.

<!-- Remove if not applicable -->



## Code Agent Policy

The Transformers repo is currently being overwhelmed by a large number of PRs and issue comments written by
code agents. We are currently bottlenecked by our ability to review and respond to them. As a result, 
**we ask that new users do not submit pure code agent PRs** at this time. 
You may use code agents in drafting or to help you diagnose issues. We'd also ask autonomous "OpenClaw"-like agents
not to open any PRs or issues for the moment.

PRs that appear to be fully agent-written will probably be closed without review, and we may block users who do this
repeatedly or maliciously. 

This is a rapidly-evolving situation that's causing significant shockwaves in the open-source community. As a result, 
this policy is likely to be updated regularly in the near future. For more information, please read [`CONTRIBUTING.md`](https://github.com/huggingface/transformers/blob/main/CONTRIBUTING.md).

- [x] I confirm that this is not a pure code agent PR.

## Before submitting
- [x] This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
- [x] Did you read the [contributor guideline](https://huggingface.co/docs/transformers/contributing) and the
      [Pull Request](https://huggingface.co/docs/transformers/pr_checks) checks?
- [ ] Was this discussed/approved via a Github issue or the [forum](https://discuss.huggingface.co/)? Please add a link
      to it if that's the case.
- [ ] Did you make sure to update the documentation with your changes according to the [guidelines](https://github.com/huggingface/transformers/tree/main/docs)?
- [ ] Did you write any new necessary [tests](https://huggingface.co/docs/transformers/testing)?


## Who can review?

Anyone in the community is free to review the PR once the tests have passed. Feel free to tag
members/contributors who may be interested in your PR.

<!-- Your PR will be replied to more quickly if you can figure out the right person to tag with @

 If you know how to use git blame, that is the easiest way, otherwise, here is a rough guide of **who to tag**.
 Please tag fewer than 3 people.

Models:

- text models: @ArthurZucker @Cyrilvallez @vasqu
- vision models: @yonigozlan @molbap
- audio models: @eustlb @ebezzam @vasqu
- multimodal models: @zucchini-nlp
- graph models: @clefourrier

Library:

- generate: @zucchini-nlp (visual-language models) or @Cyrilvallez (all others)
- continuous batching: @remi-or @ArthurZucker @McPatate
- pipelines: @Rocketknight1
- tokenizers: @ArthurZucker and @itazap
- trainer: @SunMarc
- attention: @vasqu @ArthurZucker @CyrilVallez
- model loading (from pretrained, etc): @CyrilVallez
- distributed: @3outeille @ArthurZucker
- CIs: @ydshieh

Integrations:

- ray/raytune: @richardliaw, @amogkam
- Big Model Inference: @SunMarc
- quantization: @SunMarc
- kernels: @vasqu @drbh
- peft: @BenjaminBossan @githubnemo

Devices/Backends:

- AMD ROCm: @ivarflakstad
- Intel XPU: @IlyasMoutawwakil
- Ascend NPU: @ivarflakstad 

Documentation: @stevhliu

Research projects are not maintained and should be taken as is.

 -->

Comments:
<!-- ci-dashboard-recap:start -->

---

### CI recap

**Dashboard:** [View test results in Grafana](https://transformers-ci.lor-e.huggingface.cool/d/pytest-observability-by-pr/pytest-observability-branch?var-pr=47098)
**Latest run:** [28775321391](https://github.com/huggingface/transformers/actions/runs/28775321391)
**Result:** `success` | Grafana metrics are not available yet.

<!-- ci-dashboard-recap:end -->

We're trying to cut down on small typo PRs like this right now! We'll do an agent pass to fix all of them at some point