[parser] Remove never-triggered null check in AddParameterInitializationBlock()

Change-Id: I3f150ef3424cb28c89db6ef8fcb1a3340a8ff8b1
Reviewed-on: https://chromium-review.googlesource.com/604725Reviewed-by: Marja Hölttä <marja@chromium.org>
Commit-Queue: Adam Klein <adamk@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47225}

src/parsing/parser.h

@@ -1060,7 +1060,7 @@ class V8_EXPORT_PRIVATE Parser : public NON_EXPORTED_BASE(ParserBase<Parser>) {
     if (is_async) {
       init_block = BuildRejectPromiseOnException(init_block);
     }
-    if (init_block != nullptr) body->Add(init_block, zone());
+    body->Add(init_block, zone());
   }
 
   V8_INLINE void AddFormalParameter(ParserFormalParameters* parameters,