Use TF framework
# What does this PR do?

This PR specifies `framework="tf"` for `ImageToTextPipelineTests.test_small_model_tf`.

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The pipeline tests are run in 3 docker environment: only PT, only TF, both PT/TF installation.

In the last case (`PT/TF installed`), the loaded models in tests like `test_small_model_tf` are in fact **PT models**, as we didn't specify the framework when creating the pipelines.

This is particularly confusing during debugging - especially when a model will produce diff. outputs between PT/TF models.
In such case, the same test will fail either in TF-only env. or in PT/TF env.

(One example is PR #19565, where I got the expected values from PT/TF env., and it failed on CI for TF-only env.)

**TODO**:
- Same change to other TF pipeline tests
- Investigate why we get diff. outputs between PT/TF models for `ImageToTextPipelineTests.test_small_model_tf`.



> Investigate why we get diff. outputs between PT/TF models for ImageToTextPipelineTests.test_small_model_tf.

Yup this is weird indeed, but glad we're catching such bugs !<|||||>_The documentation is not available anymore as the PR was closed or merged._<|||||>@Narsil Yes, that's why I don't want to change other places in this PR 😃 <|||||>I know what's wrong with PT v.s. TF 👀 ! 