Swift: fix tests for array concatenation

Author: rdmarsh2

swift/ql/test/library-tests/dataflow/dataflow/LocalFlow.expected

@@ -718,6 +718,8 @@
 | test.swift:650:9:650:9 | arr4 | test.swift:650:9:650:9 | SSA def(arr4) |
 | test.swift:650:16:650:23 | ... .+(_:_:) ... | test.swift:650:9:650:9 | arr4 |
 | test.swift:650:23:650:23 | arr3 | test.swift:651:15:651:15 | arr3 |
+| test.swift:651:15:651:15 | arr3 | test.swift:651:15:651:15 | &... |
+| test.swift:652:15:652:15 | arr4 | test.swift:652:15:652:15 | &... |
 | test.swift:654:9:654:9 | SSA def(arr5) | test.swift:655:15:655:15 | arr5 |
 | test.swift:654:9:654:9 | arr5 | test.swift:654:9:654:9 | SSA def(arr5) |
 | test.swift:654:16:654:51 | call to Array<Element>.init(repeating:count:) | test.swift:654:9:654:9 | arr5 |

swift/ql/test/library-tests/dataflow/dataflow/test.swift

@@ -648,8 +648,8 @@ func testArray() {
 
     var arr3 = [1]
     var arr4 = arr2 + arr3
-    sink(arg: arr3)
-    sink(arg: arr4) // $ MISSING: flow=642
+    sink(arg: arr3[0])
+    sink(arg: arr4[0]) // $ MISSING: flow=642
 
     var arr5 = Array(repeating: source(), count: 2)
     sink(arg: arr5[0]) // $ MISSING: flow=654