fix: fix validation of drag-enabled prop to avoid Vue warnings

[jledentu]

This MR fixes warning below, in 2.x branch:

[Vue warn]: Invalid prop: type check failed for prop "dragEnabled". Expected Boolean, got Function.

[codecov[bot]]

Codecov Report

Patch and project coverage have no change.

Comparison is base (a188316) 99.42% compared to head (8cc6054) 99.42%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## 2.x #205 +/- ## ======================================= Coverage 99.42% 99.42% ======================================= Files 4 4 Lines 175 175 Branches 44 44 ======================================= Hits 174 174 Misses 1 1 ``` Help us with your feedback. Take ten seconds to tell us [how you rate us](https://about.codecov.io/nps?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=J%C3%A9r%C3%A9mie+Ledentu). Have a feature suggestion? [Share it here.](https://app.codecov.io/gh/feedback/?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=J%C3%A9r%C3%A9mie+Ledentu)

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Do you have feedback about the report comment? Let us know in this issue.

[github-actions[bot]]

:tada: This PR is included in version 2.1.1 :tada:

The release is available on:

• npm package (@release-2.x dist-tag)
• GitHub release

Your semantic-release bot :package::rocket: