Removes using imports from flexfec_receiver.
Removes using imports from flexfec_receiver.

The imports of Packet, ReceivedPacket from ForwardErrorCorrection::
collides with other usages of the names introduced in a followup CL.

Bug: webrtc:9883
Change-Id: Ib042c9091ad8e350cbdf01b837af09c820dbff33
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/138279
Commit-Queue: Sebastian Jansson <c24d1bc144eb7c11e553f59153fa17dba85ca83e@webrtc.org>
Reviewed-by: Stefan Holmer <eb0877843acc39f8ef6f7269937dee931c372d23@webrtc.org>
Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#28075}

TimothyGu/libilbc,ShiftMediaProject/libilbc,TimothyGu/libilbc,ShiftMediaProject/libilbc,TimothyGu/libilbc,ShiftMediaProject/libilbc,ShiftMediaProject/libilbc,ShiftMediaProject/libilbc,TimothyGu/libilbc,TimothyGu/libilbc