Delete some more dead includes.

This breaks the cycle between Target and PluginLanguageC++, reducing
the overall cycle count from 43 to 42.

llvm-svn: 298561
diff --git a/lldb/source/Commands/CommandObjectExpression.cpp b/lldb/source/Commands/CommandObjectExpression.cpp
index cfb3a6d..8a0afce 100644
--- a/lldb/source/Commands/CommandObjectExpression.cpp
+++ b/lldb/source/Commands/CommandObjectExpression.cpp
@@ -24,7 +24,7 @@
 #include "lldb/Expression/REPL.h"
 #include "lldb/Expression/UserExpression.h"
 #include "lldb/Host/Host.h"
-#include "lldb/Host/StringConvert.h"
+#include "lldb/Host/OptionParser.h"
 #include "lldb/Interpreter/CommandInterpreter.h"
 #include "lldb/Interpreter/CommandReturnObject.h"
 #include "lldb/Symbol/ObjectFile.h"