end_line_no/end_line_pos are optional. Example SQL:
`SELECT NULL FROM {{ a_jinja_templated_table }};`
`sqlfluff lint --dialect ansi --format json` gives the following error
among others:
```
{"start_line_no": 1, "start_line_pos": 21, "code": "TMP", "description":
"Undefined jinja template variable: 'a_jinja_templated_table'", "name":
"", "warning": false}
```
As one can see there is no end_line_no/end_line_pos.
As stated in the changelog:
"the original fields of line_pos and line_no have been renamed to start_line_pos and start_line_no, to distinguish them from the new fields starting end_*"
