Fix Clang-tidy readability-redundant-string-cstr warnings

Reviewers: zturner, labath

Subscribers: tberghammer, danalbert, lldb-commits
    
Differential Revision: https://reviews.llvm.org/D26233

llvm-svn: 285855

lldb/source/Plugins/ScriptInterpreter/Python/PythonDataObjects.cpp

@@ -1021,7 +1021,7 @@ uint32_t PythonFile::GetOptionsFromMode(llvm::StringRef mode) {
   if (mode.empty())
     return 0;
 
-  return llvm::StringSwitch<uint32_t>(mode.str().c_str())
+  return llvm::StringSwitch<uint32_t>(mode.str())
       .Case("r", File::eOpenOptionRead)
       .Case("w", File::eOpenOptionWrite)
       .Case("a", File::eOpenOptionWrite | File::eOpenOptionAppend |