Remove RSA_FLAG_CACHE_PUBLIC.

This flag hasn't done anything in BoringSSL since March 2016.

Test: mma
Change-Id: I3972d7c006daa4370772363d7debf64b0c9713da
diff --git a/keystore-engine/android_engine.cpp b/keystore-engine/android_engine.cpp
index 779437d..bb0356b 100644
--- a/keystore-engine/android_engine.cpp
+++ b/keystore-engine/android_engine.cpp
@@ -199,7 +199,7 @@
     memset(&rsa_method_, 0, sizeof(rsa_method_));
     rsa_method_.common.is_static = 1;
     rsa_method_.private_transform = rsa_private_transform;
-    rsa_method_.flags = RSA_FLAG_CACHE_PUBLIC | RSA_FLAG_OPAQUE;
+    rsa_method_.flags = RSA_FLAG_OPAQUE;
     ENGINE_set_RSA_method(engine_, &rsa_method_, sizeof(rsa_method_));
 
     memset(&ecdsa_method_, 0, sizeof(ecdsa_method_));