scripted-diff: Use [[nodiscard]] (C++17) instead of NODISCARD

-BEGIN VERIFY SCRIPT-
sed -i "s/NODISCARD/[[nodiscard]]/g" $(git grep -l "NODISCARD" ":(exclude)src/bench/nanobench.h" ":(exclude)src/attributes.h")
-END VERIFY SCRIPT-

src/init.cpp

@@ -113,7 +113,7 @@ static fs::path GetPidFile(const ArgsManager& args)
     return AbsPathForConfigVal(fs::path(args.GetArg("-pid", BITCOIN_PID_FILENAME)));
 }
 
-NODISCARD static bool CreatePidFile(const ArgsManager& args)
+[[nodiscard]] static bool CreatePidFile(const ArgsManager& args)
 {
     fsbridge::ofstream file{GetPidFile(args)};
     if (file) {