wallet: unbreak with boost 1.72

wallet/walletutil.cpp:77:23: error: no member named 'level' in 'boost::filesystem::recursive_directory_iterator'
        } else if (it.level() == 0 && it->symlink_status().type() == fs::regular_file && IsBerkeleyBtree(it...
                   ~~ ^

src/fs.h

@@ -11,7 +11,6 @@
 #include <ext/stdio_filebuf.h>
 #endif
 
-#define BOOST_FILESYSTEM_NO_DEPRECATED
 #include <boost/filesystem.hpp>
 #include <boost/filesystem/fstream.hpp>