Convert argentina.cpp to utf-8 to appease clang-15

Author: eddelbuettel

ql/time/calendars/argentina.cpp

@@ -49,7 +49,7 @@ namespace QuantLib {
             || (d >= 15 && d <= 21 && w == Monday && m == June)
             // Independence Day
             || (d == 9 && m == July)
-            // Death of General José de San Martín
+            // Death of General José de San Martín
             || (d >= 15 && d <= 21 && w == Monday && m == August)
             // Columbus Day
             || ((d == 10 || d == 11 || d == 12 || d == 15 || d == 16)