SumBag: Fix typo in rotate1

This caused erroneous calls to rotateDoubleRight instead of rotateSingleRight,
thus disbalancing the tree and possibly failing to pattern match.

src/Data/SumBag.hs

@@ -135,7 +135,7 @@ balance1 a left right
     let Node _ _ lleft lright = left
         sizeLL = size lleft
         sizeLR = size lright
-    in if sizeLL < sizeLR then rotateSingleRight a left right else rotateDoubleRight a left right
+    in if sizeLR < sizeLL then rotateSingleRight a left right else rotateDoubleRight a left right
   -- No subtree is too heavy, we can just form a new tree straight away
   | otherwise = node a left right