How to use predict_oof is not given in detail

### Describe the issue linked to the documentation

The documentation for [predict_oof](https://auto.gluon.ai/stable/api/autogluon.tabular.TabularPredictor.predict_oof.html#autogluon.tabular.TabularPredictor.predict_oof) must be improved

### Suggest a potential alternative/fix

_No response_

Start with the linked TabularPredictor.predict_oof API documentation and inspect the existing entry for predict_oof. Determine which usage details are missing, then update the documentation so a reader can understand how to use the method; the issue does not name specific files or tests.

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