res_pjsip_session: Fix format_cap leak.

ASTERISK-27306

Change-Id: I2c8d3fc148f9f53715c958314e1146f9611741f3

res/res_pjsip_session.c

@@ -1547,6 +1547,7 @@ int ast_sip_session_refresh(struct ast_sip_session *session,
 						}
 					}
 					ast_stream_set_formats(stream, joint_cap);
+					ao2_cleanup(joint_cap);
 				}
 
 				++type_streams[ast_stream_get_type(stream)];