Correct assert text from r220923

Noticed in post-commit review by Adrian Prantl.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@220967 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/AsmPrinter/DwarfFile.cpp

@@ -182,7 +182,7 @@ void DwarfFile::addScopeVariable(LexicalScope *LS, DbgVariable *Var) {
       // location (eg: via a macro, or without column info, etc)) and then
       // their arguments are conflated as well.
       assert((LS->getParent() || CurNum != ArgNum) &&
-             "Missing parameter for top level (non-inlined) function");
+             "Duplicate argument for top level (non-inlined) function");
       ++I;
     }
     Vars.insert(I, Var);