Revert "Clang: Add possibility to "pgo-train" libclang with a batch file"

This reverts commit 07f4ae6227,
which broke compilation

clangbatchfileprocessor.cpp:170:27: error: ambiguous overload for
    'operator==' (operand types are 'const QChar' and 'char')

and only worked in QT_TEST=1 cases.

Change-Id: I089427359958221882cb4e4369c4b88d71779acf
Reviewed-by: Tobias Hunger <tobias.hunger@qt.io>

src/plugins/clangcodemodel/clangcodemodelplugin.h

@@ -41,9 +41,6 @@ public:
     bool initialize(const QStringList &arguments, QString *errorMessage);
     void extensionsInitialized();
 
-private:
-    void maybeHandleBatchFileAndExit() const;
-
 private:
     ModelManagerSupportProviderClang m_modelManagerSupportProvider;