gtfs-realtime.proto does not compile in protoc

[stevenb-mcgrath]

 protoc --dependency_out="C:\Users\Steven\...\deps.d" --csharp_out="C:\Users\Steven\..." --proto_path=. --proto_path="C:\Users\Steven\...protoc\include" "TransitRealtime.FeedMessage.proto"
TransitRealtime.FeedMessage.proto:630:22: "active_period" is already defined in "transit_realtime.Alert".
TransitRealtime.FeedMessage.proto:630:38: Field number 1 has already been used in "transit_realtime.Alert" by field "active_period". Next available field number is 4.

[CLAassistant]

All committers have signed the CLA.

[stevenb-mcgrath]

The issue was introduced in commit 9ad360a here: 9ad360a#diff-b0a93da1d2b3f799d4b604c4dfe28faa6cd89ff8d9eac96f9855270c1e5b4974