Add newly added PVTv2 model to all README files.
Author: robinverduijn
Pull request: yes

# What does this PR do?

Recent changes added the PVTv2 model but did not update all READMEs. This PR fixes the check_copies.py failures from [CircleCI](https://app.circleci.com/pipelines/github/huggingface/transformers/87046/workflows/eb828835-9f70-4a9f-976e-daf95311a976/jobs/1130401) by adding PVTv2 to all README files.

- Also fixes a relative path for FastSpeech2Conformer model in README_ru.md

## Before submitting
- [ ] 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://github.com/huggingface/transformers/blob/main/CONTRIBUTING.md#create-a-pull-request), Pull Request section?
- [ ] 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?
      Here are the [documentation guidelines](https://github.com/huggingface/transformers/tree/main/docs), and [here are tips on formatting docstrings](https://github.com/huggingface/transformers/tree/main/docs#writing-source-documentation).
- [ ] Did you write any new necessary tests?


## 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.

@amyeroberts @khipp @FoamoftheSea 
<!-- 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 and @younesbelkada
- vision models: @amyeroberts
- speech models: @sanchit-gandhi
- graph models: @clefourrier

Library:

- flax: @sanchit-gandhi
- generate: @gante
- pipelines: @Narsil
- tensorflow: @gante and @Rocketknight1
- tokenizers: @ArthurZucker
- trainer: @muellerzr and @pacman100

Integrations:

- deepspeed: HF Trainer/Accelerate: @pacman100
- ray/raytune: @richardliaw, @amogkam
- Big Model Inference: @SunMarc
- quantization (bitsandbytes, autogpt): @SunMarc and @younesbelkada

Documentation: @stevhliu and @MKhalusova

HF projects:

- accelerate: [different repo](https://github.com/huggingface/accelerate)
- datasets: [different repo](https://github.com/huggingface/datasets)
- diffusers: [different repo](https://github.com/huggingface/diffusers)
- rust tokenizers: [different repo](https://github.com/huggingface/tokenizers)

Maintained examples (not research project or legacy):

- Flax: @sanchit-gandhi
- PyTorch: See Models above and tag the person corresponding to the modality of the example.
- TensorFlow: @Rocketknight1

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Comments:
LGTM!

PR #29647 and PR #29574 didn't have the updated `utils/check_copies.py` file yet. Running `python utils/check_copies.py --fix_and_overwrite` on the main branch now correctly applies the changes.

The docs for this PR live [here](https://moon-ci-docs.huggingface.co/docs/transformers/pr_29647). All of your documentation changes will be reflected on that endpoint. The docs are available until 30 days after the last update.