[clang driver] Remove a bit of redundant flang specific code [nfc]

getOptionVisibilityMask already returns options::FlangOption in FlangMode,
so this assignment is entirely pointless.

Author: preames

clang/lib/Driver/Driver.cpp

@@ -1940,12 +1940,6 @@ int Driver::ExecuteCompilation(
 void Driver::PrintHelp(bool ShowHidden) const {
   llvm::opt::Visibility VisibilityMask = getOptionVisibilityMask();
 
-  // TODO: We're overriding the mask for flang here to keep this NFC for the
-  // option refactoring, but what we really need to do is annotate the flags
-  // that Flang uses.
-  if (IsFlangMode())
-    VisibilityMask = llvm::opt::Visibility(options::FlangOption);
-
   std::string Usage = llvm::formatv("{0} [options] file...", Name).str();
   getOpts().printHelp(llvm::outs(), Usage.c_str(), DriverTitle.c_str(),
                       ShowHidden, /*ShowAllAliases=*/false,