ci: run test_dataset_on_hf only for changes and every 2 days

[sam-hey]

ref: #2200
test: test_dataset_on_hf

It is just running in pr with changes in 'mteb/tasks/**.py'
or every 2 days

Code Quality

• Code Formatted: Format the code using make lint to maintain consistent style.

Documentation

• Updated Documentation: Add or update documentation to reflect the changes introduced in this PR.

Testing

• New Tests Added: Write tests to cover new functionality. Validate with make test-with-coverage.
• Tests Passed: Run tests locally using make test or make test-with-coverage to ensure no existing functionality is broken.

[isaac-chung]

@sam-hey thanks for putting this together. It looks good to me so far.

I was wondering if it would make more sense in the next iteration to run

• everything once every 2 days (ok)
• just the changed / added tasks in the PR (👈)

Would love to get @KennethEnevoldsen 's take here and on the original issue as well.

[KennethEnevoldsen]

This looks good - added a few suggestions, but nothing that changes behaviour.