ClangCodeModel: Remove unneeded code

This was liblclang-specific.

Change-Id: I3fe8a8d2d49b1c7b92a54a90864e4ead7152e4ae
Reviewed-by: Cristian Adam <cristian.adam@qt.io>

src/plugins/clangcodemodel/clangcodemodelplugin.h

@@ -24,8 +24,6 @@ public:
     void initialize() override;
 
 private:
-    void maybeHandleBatchFileAndExit() const;
-
     void generateCompilationDB();
     void createCompilationDBAction();