Bitcode: Remove an unused declaration. NFC.

llvm-svn: 299598

llvm/lib/Bitcode/Writer/BitcodeWriter.cpp

@@ -476,7 +476,6 @@ public:
   void write();
 
 private:
-  void writeIndex();
   void writeModStrings();
   void writeCombinedValueSymbolTable();
   void writeCombinedGlobalValueSummary();