Fixing documentation for cpp2 static reflection
Fixing documentation for cpp2 static reflection

Summary: there was a broken example in the docs for `reflected_struct_data_member::annotations` which this diff fixes.

Reviewed By: yfeldblum, drej82

Differential Revision: D3344469

fbshipit-source-id: 994867b38d7848a85d259d532b50c7b89fab9f95

facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,LinusU/fbthrift,LinusU/fbthrift,LinusU/fbthrift,getyourguide/fbthrift,LinusU/fbthrift,LinusU/fbthrift,facebook/fbthrift,SergeyMakarenko/fbthrift,LinusU/fbthrift,facebook/fbthrift,facebook/fbthrift,SergeyMakarenko/fbthrift,SergeyMakarenko/fbthrift,getyourguide/fbthrift,SergeyMakarenko/fbthrift,SergeyMakarenko/fbthrift,SergeyMakarenko/fbthrift,getyourguide/fbthrift,facebook/fbthrift,LinusU/fbthrift,LinusU/fbthrift,getyourguide/fbthrift,SergeyMakarenko/fbthrift,getyourguide/fbthrift,getyourguide/fbthrift,LinusU/fbthrift,SergeyMakarenko/fbthrift,facebook/fbthrift,SergeyMakarenko/fbthrift,getyourguide/fbthrift,getyourguide/fbthrift,SergeyMakarenko/fbthrift,facebook/fbthrift,LinusU/fbthrift,getyourguide/fbthrift,LinusU/fbthrift,SergeyMakarenko/fbthrift,getyourguide/fbthrift,SergeyMakarenko/fbthrift,getyourguide/fbthrift,getyourguide/fbthrift