Fix: fast strategy fallback to ocr only (#2055)
Closes #2038.
### Summary
The `fast` strategy should not fall back to a more expensive strategy.
### Testing
For
[9493801-p17.pdf](https://github.com/Unstructured-IO/unstructured/files/13292884/9493801-p17.pdf),
the following code should return an empty list.
```
elements = partition(filename=filename, strategy="fast")
```
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Co-authored-by: ryannikolaidis <1208590+ryannikolaidis@users.noreply.github.com>
Co-authored-by: christinestraub <christinestraub@users.noreply.github.com>
