`defaultGroupCapability` property requires lower case vs camelCase as documented (`groupchat` vs `groupChat`)

[nirvanatikku]

Error observed when uploading: defaultGroupCapability.groupChat | Property "groupChat" has not been defined and the schema does not allow additional properties.

Issue: note the schema uses groupchat, and docs have it camel cased: https://learn.microsoft.com/en-us/microsoftteams/platform/resources/schema/manifest-schema

It appears this is in the 1.16 schema, too. Looking through the schema, a user can provide groupchat OR groupChat and it will resolve in most cases. However, in the case of the specific property defaultGroupCapability, it does not.