VideoProjectDetails typedef

b/157517979: This part was never populated after it was added.

However, it sees non-zero traffic because there is generated client code in the wild that refers to it [1]. We keep this field and do NOT remove it because otherwise V3 would return an error when this part gets requested [2]. [1] https://developers.google.com/resources/api-libraries/documentation/youtube/v3/csharp/latest/classGoogle_1_1Apis_1_1YouTube_1_1v3_1_1Data_1_1VideoProjectDetails.html [2] http://google3/video/youtube/src/python/servers/data_api/common.py?l=1565-1569&rcl=344141677

Deprecated.