Windows: use str_format() in psutil_users().

psutil/arch/windows/sys.c

diff --git a/psutil/arch/windows/sys.c b/psutil/arch/windows/sys.c
index 612dd2e..4271a1a 100644
--- a/psutil/arch/windows/sys.c
+++ b/psutil/arch/windows/sys.c
@@ -125,9 +125,9 @@
 
         address = (PWTS_CLIENT_ADDRESS)buffer_addr;
         if (address->AddressFamily == 2) {  // AF_INET == 2
-            sprintf_s(
+            str_format(
                 address_str,
-                _countof(address_str),
+                sizeof(address_str),
                 "%u.%u.%u.%u",
                 // The IP address is offset by two bytes from the start of the
                 // Address member of the WTS_CLIENT_ADDRESS structure.