tests: bsim: bluetooth: host: privacy: peripheral: Fix scan interval

The scan interval must match scan window to start next scanning after
previous window completes. Otherwise, one of advertisements may be
missed and test will fail because it will think that RPA rotation didn't
happen in time.

Signed-off-by: Pavel Vasilyev <pavel.vasilyev@nordicsemi.no>

Author: PavelVPV

tests/bsim/bluetooth/host/privacy/peripheral/src/tester_rpa_rotation.c

@@ -134,7 +134,7 @@ void start_scanning(void)
 	struct bt_le_scan_param scan_param = {
 		.type       = BT_LE_SCAN_TYPE_PASSIVE,
 		.options    = BT_LE_SCAN_OPT_FILTER_DUPLICATE,
-		.interval   = 0x0040,
+		.interval   = 0x0020,
 		.window     = 0x0020,
 	};