fix(SankeyViz): enforce source/target order (#10003)
fix(SankeyViz): enforce source/target order (#10003)

* fix(SankeyViz): enforce source/target order

* address pr comments

* black

Co-authored-by: serena-jiang <4d12aea1e75c3f8de9f6e4e6a95f6bf09dab6344@airbnb.com>
airbnb/superset,zhouyao1994/incubator-superset,airbnb/caravel,airbnb/caravel,apache/incubator-superset,zhouyao1994/incubator-superset,apache/incubator-superset,zhouyao1994/incubator-superset,mistercrunch/panoramix,airbnb/superset,zhouyao1994/incubator-superset,zhouyao1994/incubator-superset,airbnb/superset,apache/incubator-superset,apache/incubator-superset,apache/incubator-superset,airbnb/caravel,mistercrunch/panoramix,mistercrunch/panoramix,airbnb/caravel,mistercrunch/panoramix,airbnb/superset