Address Unsaved Changes Edge Case

[QilongTang]

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Purpose

Per https://jira.autodesk.com/browse/DYN-1764, deleting a node with no connection or deleting a node which is the right end edge of the graph does not make the graph HasUnsavedChanges = true. This is due to the code in undoredo recorder to mute node modified to prevent flooding, see https://github.com/DynamoDS/Dynamo/blob/master/src/DynamoCore/Graph/Workspaces/UndoRedo.cs#L236

After some consideration, I decided to append this step to node removing step to make sure it is always done. Let me know if you have better thoughts.

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Declarations

Check these if you believe they are true

• The codebase is in a better state after this PR
• Is documented according to the standards
• The level of testing this PR includes is appropriate
• User facing strings, if any, are extracted into *.resx files
• All tests pass using the self-service CI.
• Snapshot of UI changes, if any.
• Changes to the API follow Semantic Versioning and are documented in the API Changes document.
• This PR modifies some build requirements and the readme is updated

Reviewers

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[QilongTang]

Will add one unit test soon
Unit test already added

[zeusongit]

LGTM

[reddyashish]

LGTM

[QilongTang]

Thanks @reddyashish @zeusongit for the review!