Fix a warning discovered by rL313487. [-Wunused-lambda-capture]

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@313511 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Lex/PPLexerChange.cpp

@@ -42,7 +42,7 @@ bool Preprocessor::isInPrimaryFile() const {
          "Top level include stack isn't our primary lexer?");
   return std::none_of(
       IncludeMacroStack.begin() + 1, IncludeMacroStack.end(),
-      [this](const IncludeStackInfo &ISI) -> bool { return IsFileLexer(ISI); });
+      [](const IncludeStackInfo &ISI) -> bool { return IsFileLexer(ISI); });
 }
 
 /// getCurrentLexer - Return the current file lexer being lexed from.  Note