Migrate metrics used in flax examples to Evaluate
Author: VijayKalmath
Pull request: yes

Currently, tensorflow examples use the `load_metric` function from
Datasets library,

commit migrates function call to `load` function in from Evaluate library for flax examples.

Fix for #18306

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@sgugger 

Comments:
@sgugger  , run_examples_flax successful ! Should be good to merge. 

_The documentation is not available anymore as the PR was closed or merged._

@sgugger  , I was wondering if you could point me at a good first issue I can try contributing to next. I looked at the issues and most of them seem to have folks working on them


I think there are a couples of models left where help is needed on [this issue](https://github.com/huggingface/transformers/issues/16059) if you are interested.