Fix build with Boost 1.91

Index: src/CMakeLists.txt
--- src/CMakeLists.txt.orig.port
+++ src/CMakeLists.txt
@@ -302,7 +302,6 @@ if(ENABLE_TESTS)
 		Boost::iostreams
 		Boost::program_options
 		Boost::regex
-		Boost::system
 		Boost::random
 		Boost::coroutine
 		Boost::locale
@@ -393,7 +392,6 @@ if(ENABLE_CAMPAIGN_SERVER)
 		Boost::iostreams
 		Boost::program_options
 		Boost::regex
-		Boost::system
 		Boost::random
 		Boost::coroutine
 		Boost::locale
