Clarify and unify network delay plot annotations.
Clarify and unify network delay plot annotations.

Bug: none
Change-Id: Ib66b4a926f9504cba52edf81d6afb17bb4c221ce
Reviewed-on: https://webrtc-review.googlesource.com/c/118684
Commit-Queue: Konrad Hofbauer <3c292e931896485f02beceeeebb2091226aac356@webrtc.org>
Reviewed-by: Björn Terelius <efeae16329b3cb4ac5daf80d4bfda3344c027db3@webrtc.org>
Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#26349}
TimothyGu/libilbc,ShiftMediaProject/libilbc,TimothyGu/libilbc,TimothyGu/libilbc,TimothyGu/libilbc,ShiftMediaProject/libilbc,ShiftMediaProject/libilbc,TimothyGu/libilbc,ShiftMediaProject/libilbc,ShiftMediaProject/libilbc