Use frac arg in df.sample instead of n

[abidwael]

No description provided.

[github-actions]

Unit Test Results

  6 files  +    1    6 suites  +1   23m 11s ⏱️ - 1h 24m 58s
12 tests  - 148  10 ✔️  - 133    2 💤  - 15  0 ❌ ±0 
60 runs   - 132  48 ✔️  - 121  12 💤  - 11  0 ❌ ±0 

Results for commit 29ba944. ± Comparison against base commit 999eacd.

This pull request removes 148 tests.

tests.integration_tests.test_automl ‑ test_auto_train
tests.integration_tests.test_automl ‑ test_autoconfig_preprocessing_balanced
tests.integration_tests.test_automl ‑ test_autoconfig_preprocessing_imbalanced
tests.integration_tests.test_automl ‑ test_autoconfig_preprocessing_text_image
tests.integration_tests.test_automl ‑ test_create_auto_config[image]
tests.integration_tests.test_automl ‑ test_create_auto_config[multimodal]
tests.integration_tests.test_automl ‑ test_create_auto_config[tabular_large]
tests.integration_tests.test_automl ‑ test_create_auto_config[tabular_small]
tests.integration_tests.test_automl ‑ test_create_auto_config[text]
tests.integration_tests.test_automl ‑ test_create_auto_config_with_dataset_profile
…

[justinxzhao]

Did you observe a boost in speed?

[abidwael]

Only frac is supported by dask: https://docs.dask.org/en/stable/generated/dask.dataframe.DataFrame.sample.html