proguard: reenable obfuscation

Android bundles let us keep everything together.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

app/proguard-rules.pro

@@ -1,5 +1,3 @@
 # Squelch all warnings, they're harmless but ProGuard
 # escalates them as errors.
 -dontwarn sun.misc.Unsafe
-# We're OSS anyway and who doesn't love a readable log
--dontobfuscate