[WebAssebmly] Fully disable 'protected' visibility

[sbc100]

Summary

Emscripten doesn't use protected visibility either.

clang/lib/Basic/Targets/WebAssembly.h

case CC_Swift:
       return CCCR_OK;
     default:
       return CCCR_Warning;
     }
   }
 
   bool hasExtIntType() const override { return true; }
 
-  bool hasProtectedVisibility() const override {
-    // TODO: For now, continue to advertise "protected" support for
-    // Emscripten targets.
-    return getTriple().isOSEmscripten();
-  }
+  bool hasProtectedVisibility() const override { return false; }
 };
 
 class LLVM_LIBRARY_VISIBILITY WebAssembly32TargetInfo
     : public WebAssemblyTargetInfo {
 public:
   explicit WebAssembly32TargetInfo(const llvm::Triple &T,
                                    const TargetOptions &Opts)
       : WebAssemblyTargetInfo(T, Opts) {