/usr/share/vala-0.20/vapi/gstreamer-rtsp-1.0.deps is in valac-0.20-vapi 0.20.1-2ubuntu5.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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gstreamer-1.0 gstreamer-sdp-1.0 gio-2.0