(fix) Switch order of parameters for arraySubtract on JS backends

examples/smoke/logic.ergo

@@ -22,6 +22,7 @@ contract Smoke over TemplateModel {
     enforce(some(A{ a : 1 })?.a ?? 2 = 1);
     enforce(C{ contract : "foo" }.contract = "foo");
     enforce(C{ contract : "foo" }.contract = "foo");
+    enforce(arraySubtract([1,2,3],[2,3,4]) = [1]);
     return MyResponse{
       output: "Smoke.test successful"
     }

mechanization/Backend/Lib/ENNRCtoJavaScript.v

@@ -414,7 +414,7 @@ End sanitizer.
                      | OpLt => `"(compare(" +++ e1 +++ `"," +++ e2 +++ `") < 0)" (* XXX Use compare! *)
                      | OpLe => `"(compare(" +++ e1 +++ `"," +++ e2 +++ `") <= 0)" (* XXX Use compare! *)
                      | OpBagUnion => `"bunion(" +++ e1 +++ `", " +++ e2 +++ `")"
-                     | OpBagDiff => `"bminus(" +++ e1 +++ `", " +++ e2 +++ `")"
+                     | OpBagDiff => `"bminus(" +++ e2 +++ `", " +++ e1 +++ `")"
                      | OpBagMin => `"bmin(" +++ e1 +++ `", " +++ e2 +++ `")"
                      | OpBagMax => `"bmax(" +++ e1 +++ `", " +++ e2 +++ `")"
                      | OpContains => `"contains(" +++ e1 +++ `", " +++ e2 +++ `")"