Fixes location reporting in simple-unless rule

[judithhinlung]

Background

This PR fixes #2906, a bug in the simple-unless rule in which the same value is reported for start and end line locations.

  {{#unless this.foo}}
    'Bingo!'
  {{else}}
    'Bogus!'
  {{/unless}}

**Before**:
  {
    "column": 0,
    "endColumn": 0,
    "endLine": 3,
    "filePath": "layout.hbs",
    "isFixable": true,
    "line": 3,
    "message": "Using an {{else}} block with {{unless}} should be avoided.",
    "rule": "simple-unless",
    "severity": 2,
    "source": "{{else}}",
  }

**After**:
  {
    "column": 20,
    "endColumn": 0,
    "endLine": 3,
    "filePath": "layout.hbs",
    "isFixable": true,
    "line": 1,
    "message": "Using an {{else}} block with {{unless}} should be avoided.",
    "rule": "simple-unless",
    "severity": 2,
    "source": "{{else}}",
  }


### Testing
Test Suites: 149 passed, 149 total
Tests:       5 skipped, 8540 passed, 8545 total
Snapshots:   1109 passed, 1109 total
Time:        130.081 s
Ran all test suites.
✨  Done in 140.24s.