fix(snowflake): close() swallows a failing cursor reset

[noron12234]

Problem

SnowflakeConnector.close() returns out of its finally block:

def close(self):
    try:
        self.reset_cursors()
    finally:
        if self._connection is None:
            self.logger.info("There was no connection open to be closed.")
            return                      # <-- discards the in-flight exception
        self._connection.close()
        ...

A return inside finally discards whatever exception was propagating. So if
reset_cursors() raises on a connector that never opened a connection — the
_connection is None path — the caller is told the close succeeded and the
original error is gone.

That is the exact shape that hides cursor-cleanup failures during teardown,
including inside __exit__, where the connector is closed on the way out of a
with block that may itself already be unwinding.

Fix

Replace the early return with an if/else so the finally block falls off
the end. Logged messages and the connection teardown are byte-for-byte the same;
the only behavioural change is that an exception from reset_cursors() now
reaches the caller.

Test

Added test_close_propagates_a_failing_cursor_reset next to the existing
test_close. It monkeypatches reset_cursors to raise and asserts the error
escapes close().

With the early return restored, it fails:

E       Failed: DID NOT RAISE RuntimeError

pytest src/integrations/prefect-snowflake/tests/test_database.py -k close
→ 2 passed. ruff format --check clean on both files.

[desertaxle]

LGTM!