refactor: remove unused using directives

src/qt/bitcoin.cpp

@@ -77,8 +77,6 @@ Q_DECLARE_METATYPE(CAmount)
 Q_DECLARE_METATYPE(SynchronizationState)
 Q_DECLARE_METATYPE(uint256)
 
-using node::NodeContext;
-
 static void RegisterMetaTypes()
 {
     // Register meta types used for QMetaObject::invokeMethod and Qt::QueuedConnection

src/qt/test/test_main.cpp

@@ -43,8 +43,6 @@ Q_IMPORT_PLUGIN(QAndroidPlatformIntegrationPlugin)
 #endif
 #endif
 
-using node::NodeContext;
-
 const std::function<void(const std::string&)> G_TEST_LOG_FUN{};
 
 const std::function<std::vector<const char*>()> G_TEST_COMMAND_LINE_ARGUMENTS{};