mingw: replace an obsolete link with the superseding one

The MSDN documentation has been superseded by Microsoft Docs (which is
backed by a repository on GitHub containing many, many files in Markdown
format).

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

compat/mingw.c

@@ -897,8 +897,8 @@ char *mingw_getcwd(char *pointer, int len)
 }
 
 /*
- * See http://msdn2.microsoft.com/en-us/library/17w5ykft(vs.71).aspx
- * (Parsing C++ Command-Line Arguments)
+ * See "Parsing C++ Command-Line Arguments" at Microsoft's Docs:
+ * https://docs.microsoft.com/en-us/cpp/cpp/parsing-cpp-command-line-arguments
  */
 static const char *quote_arg(const char *arg)
 {