TST Replaces pytest.warns in /cluster, /cross_decomposition, /decomposition, and /ensemble folders

[ShanDeng123]

Reference Issues/PRs
References #22572.

What does this implement/fix? Explain your changes.
Replaces the depreciating function pytest.warns(None) with warnings.catch_warnings(record=True).

Files Updated:

• test_feature_agglomeration.py
• test_optics.py
• sklearn/cross_decomposition/tests/test_pls.py
• sklearn/decomposition/tests/test_dict_learning.py
• sklearn/decomposition/tests/test_fastica.py
• sklearn/decomposition/tests/test_kernel_pca.py
• sklearn/decomposition/tests/test_pca.py
• sklearn/ensemble/tests/test_iforest.py
• sklearn/ensemble/tests/test_voting.py

Any other comments?

• Received 6 warnings when running Pytest on test_dict_learning.py
• Received 28 warnings when running Pytest on test_kernel_pca.py
• Received 17 warnings when running Pytest on test_voting.py

Unsure if these warnings are related to my updates or were preexisting...