[ELF] Remove unnecessary function call. NFC.

StringTableSection does not implement postThunkContents, so calling it on these 
sections is pointless (it calls an empty virtual function), and we can remove it.

Reviewers: ruiu

Differential Revision: https://reviews.llvm.org/D39460

llvm-svn: 317014

lld/ELF/Writer.cpp

@@ -1363,7 +1363,7 @@ template <class ELFT> void Writer<ELFT>::finalizeSections() {
     Sec->finalize<ELFT>();
 
   // createThunks may have added local symbols to the static symbol table
-  applySynthetic({InX::SymTab, InX::ShStrTab, InX::StrTab},
+  applySynthetic({InX::SymTab},
                  [](SyntheticSection *SS) { SS->postThunkContents(); });
 }