Remove stale android.arch.lifecycle Proguard flags

This library is no longer used, so remove the associated stale Proguard
keep rules.

Bug: 248580093
Test: m
Change-Id: Ia7dd977eef99c56871b9a3ca1d0046b7c76b30d9
diff --git a/proguard.flags b/proguard.flags
index 635eba6..7c71a15 100644
--- a/proguard.flags
+++ b/proguard.flags
@@ -9,17 +9,3 @@
 -keep class android.telecom.Log {
   *;
 }
-
-# Keep classes, annotations and members used by Lifecycle. Remove this once aapt2 is enabled
--keepattributes *Annotation*
-
--keep class * implements android.arch.lifecycle.LifecycleObserver {
-}
-
--keep class * implements android.arch.lifecycle.GeneratedAdapter {
-    <init>(...);
-}
-
--keepclassmembers class ** {
-    @android.arch.lifecycle.OnLifecycleEvent *;
-}