Revert "Enable R8 by default"

This reverts commit 7fbc84686c4605e87a1b81f528ae3747575372d9.

Reason for revert: Build failures on oc-mr1-dev-plus-aosp, b/70486468.

Change-Id: I8c1bf38355b1e35748e065d39038c2aaf37c64af
Exempt-From-Owner-Approval: Revert due to build failures
diff --git a/core/config.mk b/core/config.mk
index 166a371..d7e6f1e 100644
--- a/core/config.mk
+++ b/core/config.mk
@@ -546,7 +546,7 @@
 
 # Default R8 behavior when USE_R8 is not specified.
 ifndef USE_R8
-  USE_R8 := true
+  USE_R8 := false
 endif
 
 #