Do not optimize out androidplot method names by proguard.

Several audio tests use this library for plotting recorded
data. Since the library relying on reflection by method
names, we cannot obfuscated the names to make it work. See:
github.com/halfhp/androidplot/blob/master/docs/quickstart.md#add-the-dependency

Bug: 172004684
Test: CtsVerifier Hifi Ultrasound Microphone Test
Change-Id: I2da0a5ed6de1a96ed23aea0ed3d2eb75df563872
1 file changed