Remove unused Table_function_json_table::m_text_literal_cs

sql/json_table.h

@@ -260,9 +260,6 @@ class Table_function_json_table : public Sql_alloc
   /* SQL Parser: current column in JSON_TABLE (...) syntax */
   Json_table_column *m_cur_json_table_column;
 
-  /* SQL Parser: charset of the current text literal */
-  CHARSET_INFO *m_text_literal_cs;
-
 private:
   /* Context to be used for resolving the first argument. */
   Name_resolution_context *m_context;

sql/sql_yacc.yy

@@ -11581,16 +11581,9 @@ table_ref:
 
 json_text_literal:
           TEXT_STRING
-          {
-            Lex->json_table->m_text_literal_cs= NULL;
-          }
         | NCHAR_STRING
-          {
-            Lex->json_table->m_text_literal_cs= national_charset_info;
-          }
         | UNDERSCORE_CHARSET TEXT_STRING
           {
-            Lex->json_table->m_text_literal_cs= $1;
             $$= $2;
           }
         ;