fix sqlite internal tables breaking table_info (#1224)

With the current method used to get the SQL table info, sqlite internal
schema tables are being included and are not being handled correctly by
sqlalchemy because the columns have no types. This is easy to see with
the Chinook database:
```python
db = SQLDatabase.from_uri("sqlite:///Chinook.db")
print(db.table_info)
```
```python
...
sqlalchemy.exc.CompileError: (in table 'sqlite_sequence', column 'name'): Can't generate DDL for NullType(); did you forget to specify a type on this Column?
```

SQLAlchemy 2.0 [ignores these by
default](63d90b0f44/lib/sqlalchemy/dialects/sqlite/base.py (L856-L880)):

63d90b0f44/lib/sqlalchemy/dialects/sqlite/base.py (L2096-L2123)

langchain/sql_database.py

@@ -94,6 +94,7 @@ class SQLDatabase:
             tbl
             for tbl in self._metadata.sorted_tables
             if tbl.name in set(all_table_names)
+            and not (self.dialect == "sqlite" and tbl.name.startswith("sqlite_"))
         ]
 
         tables = []