Accept flow difference due to added test cases

New library gets FN for spread arguments in a call to splice(), which
was added to the old version in this PR:
  #16739

Author: asgerf

javascript/ql/test/library-tests/Arrays/DataFlow.expected

@@ -1,11 +1,11 @@
 legacyDataFlowDifference
+| arrays.js:2:16:2:23 | "source" | arrays.js:39:8:39:24 | arr4_spread.pop() | only flow with OLD data flow library |
 flow
 | arrays.js:2:16:2:23 | "source" | arrays.js:5:8:5:14 | obj.foo |
 | arrays.js:2:16:2:23 | "source" | arrays.js:11:10:11:15 | arr[i] |
 | arrays.js:2:16:2:23 | "source" | arrays.js:15:27:15:27 | e |
 | arrays.js:2:16:2:23 | "source" | arrays.js:16:23:16:23 | e |
 | arrays.js:2:16:2:23 | "source" | arrays.js:20:8:20:16 | arr.pop() |
-| arrays.js:2:16:2:23 | "source" | arrays.js:39:8:39:24 | arr4_spread.pop() |
 | arrays.js:2:16:2:23 | "source" | arrays.js:61:10:61:10 | x |
 | arrays.js:2:16:2:23 | "source" | arrays.js:65:10:65:10 | x |
 | arrays.js:2:16:2:23 | "source" | arrays.js:69:10:69:10 | x |

javascript/ql/test/library-tests/Arrays/TaintFlow.expected

@@ -1,11 +1,11 @@
 legacyDataFlowDifference
+| arrays.js:2:16:2:23 | "source" | arrays.js:39:8:39:24 | arr4_spread.pop() | only flow with OLD data flow library |
 flow
 | arrays.js:2:16:2:23 | "source" | arrays.js:5:8:5:14 | obj.foo |
 | arrays.js:2:16:2:23 | "source" | arrays.js:11:10:11:15 | arr[i] |
 | arrays.js:2:16:2:23 | "source" | arrays.js:15:27:15:27 | e |
 | arrays.js:2:16:2:23 | "source" | arrays.js:16:23:16:23 | e |
 | arrays.js:2:16:2:23 | "source" | arrays.js:20:8:20:16 | arr.pop() |
-| arrays.js:2:16:2:23 | "source" | arrays.js:39:8:39:24 | arr4_spread.pop() |
 | arrays.js:2:16:2:23 | "source" | arrays.js:58:8:58:13 | arr[0] |
 | arrays.js:2:16:2:23 | "source" | arrays.js:61:10:61:10 | x |
 | arrays.js:2:16:2:23 | "source" | arrays.js:65:10:65:10 | x |