Fix `test_load_default_pipelines_tf` test error
# What does this PR do?

My change in #18292 needs to add `tf` under `default` key (for `image-classification`), otherwise we have 

```bash
FAILED tests/pipelines/test_pipelines_common.py::PipelineUtilsTest::test_load_default_pipelines_tf
```
with error message
```bash
         else:
             # normal case - non-translation pipeline
 >           model_id, revision = task_dict["default"]["model"][framework]
 E           KeyError: 'tf'
```


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