remove std::filesystem usage to make old compilers happy

src/justify.cpp

@@ -29,7 +29,6 @@
 #include <unistd.h>
 
 #include <cstdlib>
-#include <filesystem>
 #include <fstream>
 #include <iostream>
 #include <memory>
@@ -260,12 +259,6 @@ bool justify(const Settings& settings)
     }
     else
     {
-        if (!std::filesystem::exists(settings.inFile))
-        {
-            std::cerr << "Input file \"" << settings.inFile << "\" "
-                      << "not found." << std::endl;
-            return false;
-        }
         try
         {
             inputFile.open(settings.inFile, std::ifstream::in);