Remove UpdateManager mention in integration docs

[QilongTang]

Purpose

Remove UpdateManager mention in integration docs since the class has been removed as part of Dynamo 3.0

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
• This PR contains no files larger than 50 MB

Release Notes

Remove UpdateManager mention in integration docs since the class has been removed as part of Dynamo 3.0

Reviewers

FYIs

@DynamoDS/dynamo