[lldb][ClangExpressionParser][NFC] Remove unused local vars

These got removed in `d6cbcf93b227befaad00957a56acd63c837c26ff` but
mistakenly added back when rebasing `12e3a06cb7615fbd91031420f3dec2a85d7877d6`

(cherry picked from commit f05efd0)

Author: Michael137

lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionParser.cpp

@@ -625,10 +625,6 @@ ClangExpressionParser::ClangExpressionParser(
   // Make sure clang uses the same VFS as LLDB.
   m_compiler->createFileManager(FileSystem::Instance().GetVirtualFileSystem());
 
-  std::string abi;
-  ArchSpec target_arch;
-  target_arch = target_sp->GetArchitecture();
-
   // 2. Configure the compiler with a set of default options that are
   // appropriate for most situations.
   SetupTargetOpts(*m_compiler, *target_sp);