Add missed project namespace to generator config

Fixes: #184

src/generator/GeneratorConfig.cmake.in

@@ -4,7 +4,7 @@ if(NOT TARGET @TARGET@ AND NOT @TARGET@_BINARY_DIR)
     include("${CMAKE_CURRENT_LIST_DIR}/@TARGET_EXPORT@.cmake")
 endif()
 
-set_property(TARGET @TARGET@ PROPERTY PROTO_PARSER "${CMAKE_CURRENT_LIST_DIR}/parsemessages.go")
+set_property(TARGET @QT_PROTOBUF_PROJECT@::@TARGET@ PROPERTY PROTO_PARSER "${CMAKE_CURRENT_LIST_DIR}/parsemessages.go")
 
 @PACKAGE_INIT@
 set(GENERATOR_TARGET "@GENERATOR_TARGET@")