blink_gc_plugin: Update stack_allocated test expectations

The test broke after crrev.com/802490

TBR=thakis

Bug: 1100257, 1123469
Change-Id: Ie8ae2f26b1ffd92fa422d719a80aecc161f18738
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2382836Reviewed-by: Hans Wennborg <hans@chromium.org>
Commit-Queue: Hans Wennborg <hans@chromium.org>
Cr-Commit-Position: refs/heads/master@{#803056}

tools/clang/blink_gc_plugin/tests/stack_allocated.txt

@@ -23,7 +23,7 @@ class DerivedHeapObject2 : public HeapObject {
 ./stack_allocated.h:44:3: warning: [blink-gc] Garbage collected class 'DerivedHeapObject2' is not permitted to override its new operator.
   STACK_ALLOCATED();
   ^
-./heap/stubs.h:189:5: note: expanded from macro 'STACK_ALLOCATED'
+./heap/stubs.h:188:5: note: expanded from macro 'STACK_ALLOCATED'
     __attribute__((annotate("blink_stack_allocated")))      \
     ^
 In file included from stack_allocated.cpp:5: