yuzu-tester/yuzu: Remove unused variable

Gets rid of a compilation warning.

src/yuzu_tester/yuzu.cpp

@@ -92,7 +92,6 @@ int main(int argc, char** argv) {
 
     int option_index = 0;
 
-    char* endarg;
 #ifdef _WIN32
     int argc_w;
     auto argv_w = CommandLineToArgvW(GetCommandLineW(), &argc_w);