Removing graphviz pin in windows ci

[freddyaboulton]

Pull Request Description

Fixes #1848

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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 #1851 (a42e1da) into main (12a5456) will increase coverage by 67.0%.
The diff coverage is n/a.

@@           Coverage Diff            @@
##            main   #1851      +/-   ##
========================================
+ Coverage   32.9%   99.9%   +67.0%     
========================================
  Files        255     255              
  Lines      20662   20662              
========================================
+ Hits        6795   20631   +13836     
+ Misses     13867      31   -13836     

Impacted Files	Coverage Δ
evalml/tests/utils_tests/test_dependencies.py	87.5% <0.0%> (+87.5%)	⬆️
evalml/tests/component_tests/test_utils.py	98.3% <0.0%> (+98.3%)	⬆️
...ests/automl_tests/test_automl_search_regression.py	99.2% <0.0%> (+99.2%)	⬆️
evalml/tests/component_tests/test_components.py	99.2% <0.0%> (+99.2%)	⬆️
...understanding_tests/test_permutation_importance.py	99.3% <0.0%> (+99.3%)	⬆️
evalml/tests/pipeline_tests/test_pipelines.py	99.6% <0.0%> (+99.6%)	⬆️
.../automl_tests/test_automl_search_classification.py	99.7% <0.0%> (+99.7%)	⬆️
...lml/tests/model_understanding_tests/test_graphs.py	99.8% <0.0%> (+99.8%)	⬆️
evalml/__main__.py	100.0% <0.0%> (+100.0%)	⬆️
evalml/tests/utils_tests/test_logger.py	100.0% <0.0%> (+100.0%)	⬆️
... and 88 more

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[bchen1116]

🚀🚀🚀

[angela97lin]

🥳 🎈

[ParthivNaresh]

Beautiful!