Remove extra no_gc declaration

No-tree-checks: true
No-try: true
Change-Id: I7f2d5806a94f381849e395f590f943eb8b1a0196
Reviewed-on: https://chromium-review.googlesource.com/c/1350994
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Reviewed-by: Maya Lekova <mslekova@chromium.org>
Cr-Commit-Position: refs/heads/master@{#57833}

src/builtins/builtins-string.cc

@@ -468,7 +468,6 @@ V8_WARN_UNUSED_RESULT static Object* ConvertCase(
     String::FlatContent flat_content = s->GetFlatContent();
     DCHECK(flat_content.IsFlat());
     bool has_changed_character = false;
-    DisallowHeapAllocation no_gc;
     int index_to_first_unprocessed = FastAsciiConvert<Converter::kIsToLower>(
         reinterpret_cast<char*>(result->GetChars()),
         reinterpret_cast<const char*>(flat_content.ToOneByteVector().start()),