Delete an (apparently unused) global in ClangExpressionVaraible.cpp

[ldrumm]

Summary

I've grepped the entire llvm source tree, and can't find any external references, to this symbol.

The build is also clean without it, so I think this is safe to remove.

source/Plugins/ExpressionParser/Clang/ClangExpressionVariable.cpp

 #include "lldb/Core/ValueObjectConstResult.h"
 #include "lldb/Target/ExecutionContext.h"
 #include "lldb/Target/Process.h"
 #include "clang/AST/ASTContext.h"
 
 using namespace lldb_private;
 using namespace clang;
 
-const char *g_clang_expression_variable_kind_name = "ClangExpressionVariable";
-
 ClangExpressionVariable::ClangExpressionVariable(
     ExecutionContextScope *exe_scope, lldb::ByteOrder byte_order,
     uint32_t addr_byte_size)
     : ExpressionVariable(LLVMCastKind::eKindClang), m_parser_vars(),
       m_jit_vars() {
   m_flags = EVNone;
   m_frozen_sp =
       ValueObjectConstResult::Create(exe_scope, byte_order, addr_byte_size);