Swift: modify test so implicit read isn't needed at sink

Author: rdmarsh2

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

@@ -746,6 +746,7 @@
 | test.swift:663:9:663:9 | f | test.swift:663:9:663:9 | SSA def(f) |
 | test.swift:663:13:663:29 | #keyPath(...) | test.swift:663:9:663:9 | f |
 | test.swift:663:13:663:29 | enter #keyPath(...) | test.swift:663:26:663:26 | KeyPathComponent |
+| test.swift:664:15:664:28 | \\...[...] | test.swift:664:15:664:29 | ...! |
 | test.swift:668:9:668:9 | SSA def(x) | test.swift:672:9:672:9 | x |
 | test.swift:668:9:668:9 | x | test.swift:668:9:668:9 | SSA def(x) |
 | test.swift:668:13:668:20 | call to source() | test.swift:668:9:668:9 | x |

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

@@ -661,7 +661,7 @@ func testOptionalKeyPath() {
     let s = S(x: source())
     let s2 = S2_Optional(s: s)
     let f = \S2_Optional.s?.x
-    sink(opt: s2[keyPath: f]) // $ MISSING: flow=661
+    sink(arg: s2[keyPath: f]!) // $ MISSING: flow=661
 }
 
 func testSwap() {