libbinder: hide kDefaultMaxOutgoingConnections

We don't need to expose this.

Bug: 270374393
Test: N/A
Change-Id: I166f3d78ab2c3a3ed728d18b9b7a289a2bdc9815
diff --git a/libs/binder/include/binder/RpcSession.h b/libs/binder/include/binder/RpcSession.h
index 3082427..0750ccf 100644
--- a/libs/binder/include/binder/RpcSession.h
+++ b/libs/binder/include/binder/RpcSession.h
@@ -54,8 +54,6 @@
  */
 class RpcSession final : public virtual RefBase {
 public:
-    static constexpr size_t kDefaultMaxOutgoingConnections = 10;
-
     // Create an RpcSession with default configuration (raw sockets).
     static sp<RpcSession> make();
 
@@ -223,6 +221,8 @@
     friend RpcState;
     explicit RpcSession(std::unique_ptr<RpcTransportCtx> ctx);
 
+    static constexpr size_t kDefaultMaxOutgoingConnections = 10;
+
     // internal version of setProtocolVersion that
     // optionally skips the mStartedSetup check
     [[nodiscard]] bool setProtocolVersionInternal(uint32_t version, bool checkStarted);