Corrected config field for filtering cucumber scenarios by tag (#3695)
Corrected config field for filtering cucumber scenarios by tag (#3695)

## Proposed changes

The field was `tagExpression` then changed to `tags` (https://github.com/webdriverio/wdio-cucumber-framework/commit/0b7e63032f7234dfa5f6383c9762d8c7288f2d26) and then changed back to `tagExpression` (https://github.com/webdriverio/wdio-cucumber-framework/pull/127)

This change changes the config file documentation accordingly. 👍

## Types of changes

- [x] Bugfix (non-breaking change which fixes an issue)
- [ ] New feature (non-breaking change which adds functionality)
- [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)

## Checklist

- [x] I have read the [CONTRIBUTING](https://github.com/webdriverio/webdriverio/blob/master/CONTRIBUTING.md) doc
- [ ] I have added tests that prove my fix is effective or that my feature works
- [x] I have added necessary documentation (if appropriate)

## Further comments

None

### Reviewers: @webdriverio/technical-committee
webdriverio/webdriverio,webdriverio/webdriverio,webdriverio/webdriverio