tests: fix test_tcp_ssl_version_mismatch

It was broken since 7783e0b. This change was added there by mistake and
in fact didn't change anything for Python 3.12. Instead, it seems to
have hidden a bug that revealed itself with Python 3.13.

This commit reverts the change that broke the test.

Signed-off-by: Mikhail Koviazin <mikhail.koviazin@aiven.io>

tests/test_connect.py

@@ -141,7 +141,7 @@ def test_tcp_ssl_version_mismatch(tcp_address):
             tcp_address,
             certfile=certfile,
             keyfile=keyfile,
-            ssl_version=ssl.TLSVersion.TLSv1_3,
+            ssl_version=ssl.TLSVersion.TLSv1_2,
         )