PR comment feature should be opt-in and not enabled by default

[praneetloke]

This PR should fix #118. The default value for the PR comment input should be false and the default value for using threaded comments should be true. These were flipped unfortunately when the feature was added, which caused release pipelines to fail since the task was throwing an error about the lack of a PR ID.

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• [x] If you changed the values of the properties name, publisher, and galleryFlags in the vss-extension.json file, you have reverted them.
• [x] If you changed the values of the properties id, name, author, you have reverted them.
• [x] I have reverted any changes to the version number components in both vss-extension.json and task.json, OR I didn't change them.

[AaronFriel]

/azp run

[azure-pipelines[bot]]

Azure Pipelines successfully started running 3 pipeline(s).

[AaronFriel]

/azp run

[azure-pipelines[bot]]

Azure Pipelines successfully started running 3 pipeline(s).

[AaronFriel]

/azp run

[azure-pipelines[bot]]

Azure Pipelines successfully started running 1 pipeline(s).

[AaronFriel]

/azp run

[azure-pipelines[bot]]

Azure Pipelines successfully started running 1 pipeline(s).