libbinder: remove unused 'pool' var

originally pointed out by elsk@

Bug: N/A
Test: N/A
Change-Id: I5fa0f90db4f30cad060b6e5d5794a8f0c8255637
diff --git a/libs/binder/RpcServer.cpp b/libs/binder/RpcServer.cpp
index aaebb23..9fa053d 100644
--- a/libs/binder/RpcServer.cpp
+++ b/libs/binder/RpcServer.cpp
@@ -121,8 +121,6 @@
 
 void RpcServer::join() {
     LOG_ALWAYS_FATAL_IF(!mAgreedExperimental, "no!");
-
-    std::vector<std::thread> pool;
     {
         std::lock_guard<std::mutex> _l(mLock);
         LOG_ALWAYS_FATAL_IF(mServer.get() == -1, "RpcServer must be setup to join.");