Resolve "Migrate app/views/ci/variables/_variable_row.html.haml to Pajamas::ButtonComponent"

What does this MR do and why?

Updates the remove button on the row of variables in /-/pipeline_schedules/new to use the Pajamas button component

Screenshots or screen recordings

Before	After

How to set up and validate locally

1. Go to "CI/CD > Schedules"
2. Create a new schedule
3. Add a new variable by selecting a variable type from the dropdown
4. A new variable row should appear
5. Confirm that the x close button exists
6. Confirm that clicking on the close button removes the variable

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #363911 (closed)