Fix Web IDE button style inconsistency

What does this MR do?

When working on the Gitpod button integration we introduced a gl-button-deprecated-adapter class to help promote style consistency. Looks like this needed to be applied at 1 level higher.

Screenshots (strongly suggested)

Before (master and .com)	After (this MR)	Also looks good with Gitpod dropdown

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content