Python: Update rest of tests to new dataflow lib

I had missed these originally, since I had just fixed the ones that were
highlighted in the actions logs, thinking they had covered everything :(

python/ql/test/experimental/dataflow/basic/sinks.ql

@@ -2,6 +2,6 @@ import allFlowsConfig
 
 from DataFlow::Node sink
 where
-  exists(AllFlowsConfig cfg | cfg.isSink(sink)) and
+  AllFlowsConfig::isSink(sink) and
   exists(sink.getLocation().getFile().getRelativePath())
 select sink