test: fix over-dependence on native promise impl

In later versions of V8, the stack trace will be different than our
current expectations for Promise methods.

PR-URL: https://github.com/nodejs/node/pull/11437
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Evan Lucas <evanlucas@me.com>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>

test/message/unhandled_promise_trace_warnings.out

@@ -23,8 +23,8 @@
     at getAsynchronousRejectionWarningObject (internal/process/promises.js:*)
     at rejectionHandled (internal/process/promises.js:*)
     at *
-    at Promise.then (native)
-    at Promise.catch (native)
+    at Promise.then *
+    at Promise.catch *
     at Immediate.setImmediate (*test*message*unhandled_promise_trace_warnings.js:*)
     at *
     at *