Pin scikit-optimize to version 0.7.4

[freddyaboulton]

Pull Request Description

The latest version of scikit-optimize breaks AutoML. This PR pins the version to not exceed 0.7.4. We may upgrade the latest version when we get to #1121

I don't think performance tests are necessary for this change since we are not upgrading any dependency versions.

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After creating the pull request: in order to pass the release_notes_updated check you will need to update the "Future Release" section of docs/source/release_notes.rst to include this pull request by adding :pr:123.

[codecov]

Codecov Report

Merging #1136 into main will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##             main    #1136     +/-   ##
=========================================
  Coverage   99.91%   99.91%             
=========================================
  Files         183      195     +12     
  Lines       10143    11159   +1016     
=========================================
+ Hits        10134    11150   +1016     
  Misses          9        9             

Impacted Files	Coverage Δ
evalml/demos/breast_cancer.py	100.00% <ø> (ø)
..._understanding/prediction_explanations/__init__.py	100.00% <ø> (ø)
...alml/objectives/binary_classification_objective.py	100.00% <ø> (ø)
evalml/pipelines/__init__.py	100.00% <ø> (ø)
evalml/pipelines/components/__init__.py	100.00% <ø> (ø)
evalml/pipelines/components/estimators/__init__.py	100.00% <ø> (ø)
evalml/__init__.py	100.00% <100.00%> (ø)
evalml/automl/automl_search.py	99.56% <100.00%> (+<0.01%)	⬆️
evalml/data_checks/invalid_targets_data_check.py	100.00% <100.00%> (ø)
evalml/demos/__init__.py	100.00% <100.00%> (ø)
... and 70 more

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[jeremyliweishih]