Strip trailing whitespace from prompt file

Many/most text editors save with trailing whitespace.

utils.cpp

@@ -33,6 +33,10 @@ bool gpt_params_parse(int argc, char ** argv, gpt_params & params) {
                     std::istreambuf_iterator<char>(),
                     back_inserter(params.prompt));
 
+            std::string& p = params.prompt;
+            p.erase(std::find_if(p.rbegin(), p.rend(), [](unsigned char ch) {
+                return !std::isspace(ch);
+            }).base(), p.end());
         } else if (arg == "-n" || arg == "--n_predict") {
             params.n_predict = std::stoi(argv[++i]);
         } else if (arg == "--top_k") {