binderRpcTest: conditional experimental protocol

Previously this test failed in REL mode and required a
change. This was done so that we made sure to freeze it for
release. Now that we have TARGET_RELEASE, we need to make this
conditional.

Bug: 305786304
Test: binderRpcTest on '-next' configuration
Change-Id: I726c71399c7e469698abc630a006ce089dc4bca8
diff --git a/libs/binder/RpcState.cpp b/libs/binder/RpcState.cpp
index bac2808..f9e833b 100644
--- a/libs/binder/RpcState.cpp
+++ b/libs/binder/RpcState.cpp
@@ -409,10 +409,11 @@
         char codename[PROPERTY_VALUE_MAX];
         property_get("ro.build.version.codename", codename, "");
         if (!strcmp(codename, "REL")) {
-            ALOGE("Cannot use experimental RPC binder protocol on a release branch.");
+            ALOGE("Cannot use experimental RPC binder protocol in a release configuration.");
             return false;
         }
 #else
+        // TODO(b/305983144)
         // don't restrict on other platforms, though experimental should
         // only really be used for testing, we don't have a good way to see
         // what is shipping outside of Android