Fix a few -Wignored-qualifiers warnings.

src/compiler/code-generator.h

Index: src/compiler/code-generator.h
diff --git a/src/compiler/code-generator.h b/src/compiler/code-generator.h
index 59a5af9a0703597ebe51c09bb72c030caecd34f6..f0a59eeeae3e080ed1090f372351a1eacb010377 100644
--- a/src/compiler/code-generator.h
+++ b/src/compiler/code-generator.h
@@ -39,7 +39,7 @@ class CodeGenerator final : public GapResolver::Assembler {
 
   InstructionSequence* code() const { return code_; }
   FrameAccessState* frame_access_state() const { return frame_access_state_; }
-  Frame* const frame() const { return frame_access_state_->frame(); }
+  Frame* frame() const { return frame_access_state_->frame(); }
   Isolate* isolate() const { return info_->isolate(); }
   Linkage* linkage() const { return linkage_; }