Set gtest_enable_absl_printers to true.
Set gtest_enable_absl_printers to true.

Starting from [1], gtest can pretty print absl types. In order to
enable the feature WebRTC has to set gtest_enable_absl_printers to true
in the .gn file.

[1] - https://chromium-review.googlesource.com/c/chromium/src/+/1027711

Bug: None
Change-Id: I74eb9a48c361f1523dd8d45510297e101a4d14cd
Reviewed-on: https://webrtc-review.googlesource.com/85345
Reviewed-by: Karl Wiberg <2c708eb0a58047bf403399f50b3da33ffd2dd444@webrtc.org>
Commit-Queue: Mirko Bonadei <d2c43c210eae6feef04f53bae50885e8152edcca@webrtc.org>
Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#23781}
TimothyGu/libilbc,TimothyGu/libilbc,TimothyGu/libilbc,TimothyGu/libilbc,ShiftMediaProject/libilbc,ShiftMediaProject/libilbc,ShiftMediaProject/libilbc,ShiftMediaProject/libilbc,ShiftMediaProject/libilbc,TimothyGu/libilbc