[CodeGen] Fix a warning

This patch fixes:

  clang/lib/CodeGen/CGOpenMPRuntime.cpp:6098:8: error: lambda capture
  'this' is not used [-Werror,-Wunused-lambda-capture]

Author: kazutakahirata

clang/lib/CodeGen/CGOpenMPRuntime.cpp

@@ -6095,7 +6095,7 @@ void CGOpenMPRuntime::emitTargetOutlinedFunctionHelper(
 
   CodeGenFunction CGF(CGM, true);
   llvm::OpenMPIRBuilder::FunctionGenCallback &&GenerateOutlinedFunction =
-      [this, &CGF, &D, &CodeGen](StringRef EntryFnName) {
+      [&CGF, &D, &CodeGen](StringRef EntryFnName) {
         const CapturedStmt &CS = *D.getCapturedStmt(OMPD_target);
 
         CGOpenMPTargetRegionInfo CGInfo(CS, CodeGen, EntryFnName);