Remove an unnecessary variable.

Found using Clang's static analyzer.

Modules/_sqlite/connection.c

@@ -745,7 +745,6 @@ void _pysqlite_final_callback(sqlite3_context* context)
 {
     PyObject* function_result = NULL;
     PyObject** aggregate_instance;
-    PyObject* aggregate_class;
 
 #ifdef WITH_THREAD
     PyGILState_STATE threadstate;
@@ -753,8 +752,6 @@ void _pysqlite_final_callback(sqlite3_context* context)
     threadstate = PyGILState_Ensure();
 #endif
 
-    aggregate_class = (PyObject*)sqlite3_user_data(context);
-
     aggregate_instance = (PyObject**)sqlite3_aggregate_context(context, sizeof(PyObject*));
     if (!*aggregate_instance) {
         /* this branch is executed if there was an exception in the aggregate's