Move Pipelines quota to Pipelines (CI/CD) in Settings page for groups

Description

For groups, we have pipelines quota as a standalone page under settings.

Since we now have Settings > Pipelines (will be Settings > CI/CD) for group-level variables, we can consider to move pipelines quota in the same submenu.

Proposal

Move Settings > Pipelines quota in Settings > Pipelines

Feature checklist

Make sure these are completed before closing the issue, with a link to the relevant commit.