Fix condition expression input layout

[azeghers]

Solution

The element was missing a class defining the layout of the x clear button

Which issue does this PR address?

Closes https://github.com/zeebe-io/zeebe-modeler/issues/268

Acceptance Criteria

• [ ] Corresponds to the concept
• [ ] Corresponds to the design

Definition of Done

• [ ] corresponds to the design principles
• [ ] corresponds to the code standards
• [ ] passes Continuous Integration checks
• [ ] available as feature branch on GitHub
  • [ ] contains the cleaned up commit history
  • [ ] commit messages satisfy our commit message guidelines
  • [ ] a single commit closes the issue via Closes #issuenr

[pinussilvestrus]

If this is a fix, we should direct the PR to master. Or is not broken on master?

[azeghers]

It is branched from master, github simply defaults to develop and I didn't notice