Bump ember-modifier from 1.0.3 to 2.1.0

Bumps [ember-modifier](https://github.com/ember-modifier/ember-modifier) from 1.0.3 to 2.1.0.
- [Release notes](https://github.com/ember-modifier/ember-modifier/releases)
- [Changelog](https://github.com/ember-modifier/ember-modifier/blob/master/CHANGELOG.md)
- [Commits](ember-modifier/ember-modifier@1.0.3...v2.1.0)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Author: dependabot-preview[bot]