Fixes spacing for buttons in pipeline wizard

What does this MR do and why?

Fixes spacing for the "Back" and "Next" button in the Pipeline Wizard.

Before	After

How to set up and validate locally

Make sure that use_pipeline_wizard_for_pages feature flag is enabled.

Feature.enable(:use_pipeline_wizard_for_pages)

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.