message: update slqite datetime format doc
diff: @@ -23,7 +23,7 @@ cx.read_sql(conn, query) # read data from Big
  | BLOB | object | declared type that contains substring "blob" |
  | DATE | datetime64[ns] | declared type is "date" |
  | TIME | object | declared type is "time" |
  -| TIMESTAMP | datetime64[ns] | declared type is "datetime" or "timestamp" |
  +| TIMESTAMP | datetime64[ns] | declared type is "datetime" or "timestamp", the format must follow `YYYY-MM-DD HH:MM:SS"/"YYYY-MM-DD HH:MM:SS.SSS`|
  ## Performance (r5.4xlarge EC2 same instance)
  