Use mediadrm from private instead of tangorpro

* Private mediadrm: ag/29478046, ag/29489024

Bug: 367906184
Bug: 366426322
Flag: EXEMPT castauth enabled
Test: b/367906184#comment5
Change-Id: I8dc459ca757de0efd0e989adf92dcb0f4bf5519d

cast_auth/mediadrm/CreatePluginFactories.cpp

@@ -1,17 +0,0 @@
-#include "CreatePluginFactories.h"
-
-namespace aidl {
-namespace android {
-namespace hardware {
-namespace drm {
-namespace castkey {
-
-std::shared_ptr<DrmFactory> createDrmFactory() {
-    return ::ndk::SharedRefBase::make<DrmFactory>();
-}
-
-}  // namespace castkey
-}  // namespace drm
-}  // namespace hardware
-}  // namespace android
-}  // namespace aidl