Add type to distinguish gitlab diff note and discussion note

[jonathanlam]

Description

this field is in the DiffNote and DiscussionNote webhooks and allows us to distinguish a comment left on a code review vs a comment on the main Pull request

Checklist

• I have added one of the patch, minor, major or no-release labels
• I have linked an issue from this repository using the Development option
• I have performed a self-review of my own code
• I have checked for redundant or commented out code
• I have commented my code where I can't make it self-documenting
• I have made corresponding changes to the documentation
• I have added any appropriate tests

[coveralls]

Pull Request Test Coverage Report for Build 12858841588

Details

• 23 of 26 (88.46%) changed or added relevant lines in 2 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.2%) to 88.583%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
azuredevops/azuredevops.go	19	22	86.36%

Totals
Change from base Build 10594209340:	0.2%
Covered Lines:	900
Relevant Lines:	1016

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💛 - Coveralls