Replace includes of boost/filesystem.h with fs.h

This is step one in abstracting the use of boost::filesystem.

src/qt/test/rpcnestedtests.cpp

@@ -6,6 +6,7 @@
 
 #include "chainparams.h"
 #include "consensus/validation.h"
+#include "fs.h"
 #include "validation.h"
 #include "rpc/register.h"
 #include "rpc/server.h"
@@ -17,8 +18,6 @@
 #include <QDir>
 #include <QtGlobal>
 
-#include <boost/filesystem.hpp>
-
 static UniValue rpcNestedTest_rpc(const JSONRPCRequest& request)
 {
     if (request.fHelp) {