Bug fix in reorderStmts

Summary:
Tracking of bound variables was wrong. This hopefully shouldn't change
any existing test cases or perf, but it was exposed by other changes
I'm making in subsequent diffs.

Reviewed By: malanka

Differential Revision: D64036030

fbshipit-source-id: a39974e77922cbded5924d77e42a6963784cd2e4

glean/db/Glean/Query/Reorder.hs

@@ -191,7 +191,7 @@ reorderGroup g = do
       (stmts'',bound'') <- go bound' rest
       return (FlatDisjunction [g'] : stmts'', bound'')
     go bound (stmt : rest) = do
-      (stmts', bound') <- go (IntSet.union (vars stmt) bound) rest
+      (stmts', bound') <- go (IntSet.union (boundVars stmt) bound) rest
       return (stmt : stmts', bound')
 
     squash [] = []