Use snprintf instead of sprintf for get_ssl_library_version

This is avoid a warning/error (when using -Werror) under current macOS
of sprintf:

   __deprecated_msg("This function is provided for compatibility
   reasons only.  Due to security concerns inherent in the design
   of sprintf(3), it is highly recommended that you use snprintf(3)
   instead.")

Change-Id: I3c6fd36eb9daee9244d6dc6d9f22de1c5cf9d039
Signed-off-by: Arne Schwabe <arne-openvpn@rfc2549.org>
Acked-by: Frank Lichtenheld <frank@lichtenheld.com>
Message-Id: <20240325125052.14135-1-gert@greenie.muc.de>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg28458.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>

src/openvpn/ssl_mbedtls.c

@@ -1614,7 +1614,7 @@ get_ssl_library_version(void)
 {
     static char mbedtls_version[30];
     unsigned int pv = mbedtls_version_get_number();
-    sprintf( mbedtls_version, "mbed TLS %d.%d.%d",
+    snprintf(mbedtls_version, sizeof(mbedtls_version), "mbed TLS %d.%d.%d",
              (pv>>24)&0xff, (pv>>16)&0xff, (pv>>8)&0xff );
     return mbedtls_version;
 }