curl_multibyte: remove access() function wrapper for Windows

- Remove curlx_win32_access() which was a wrapper to use access() in
  Windows.

This is a follow-up to 602fc213, one of two commits which removed
access() calls from the codebase and banned use of the function.

Closes https://github.com/curl/curl/pull/13529

lib/curl_multibyte.c

@@ -159,21 +159,4 @@ int curlx_win32_stat(const char *path, struct_stat *buffer)
 #endif
 }
 
-int curlx_win32_access(const char *path, int mode)
-{
-#if defined(_UNICODE)
-  int result = -1;
-  wchar_t *path_w = curlx_convert_UTF8_to_wchar(path);
-  if(path_w) {
-    result = _waccess(path_w, mode);
-    curlx_unicodefree(path_w);
-  }
-  else
-    errno = EINVAL;
-  return result;
-#else
-  return _access(path, mode);
-#endif
-}
-
 #endif /* USE_WIN32_LARGE_FILES || USE_WIN32_SMALL_FILES */