bug(connections): sslmode=disable in URI does not force useSSL=false

[ZhuchkaTriplesix]

connection_url_parser.dart does not reset useSSL when the URI contains sslmode=disable. The default is false, so it usually works, but if the parser is reused or defaults change the flag can remain stale.

Impact: The persisted use_ssl boolean can contradict the URI intent.

Expected: Explicit sslmode=disable in the URI must set useSSL = false.

Acceptance criteria:

• sslmode=disable always produces useSSL = false.
• Add unit test.