feat(eui): remove xl size from EuiTabs

[weronikaolejniczak]

Summary

[!IMPORTANT] This is a breaking change.

Closes https://github.com/elastic/eui/issues/8302

On this PR, I:

• feat(eui): remove xl size from EuiTabs
• chore(eui): update snapshot tests

Kibana impact

There are no usages in Kibana of EuiTabs with xl size (search) or EuiPageHeader / KibanaPageTemplate.Header with tabs but no pageTitle.

Cloud UI impact

There are no usages in Cloud UI of EuiTabs with xl size (search) or EuiPageHeader with tabs but no pageTitle.

QA

Specific checklist

• [x] EUI builds with no errors
• [x] Unit tests pass
• [ ] The Kibana and Cloud UI affected usages list is correct

General checklist

• Browser QA
  • [ ] ~Checked in both light and dark modes~
  • [ ] ~Checked in both MacOS and Windows high contrast modes~
    • (emulate forced colors if you do not have access to a Windows machine.)
  • [ ] ~Checked in mobile~
  • [ ] ~Checked in Chrome, Safari, Edge, and Firefox~
  • [ ] ~Checked for accessibility including keyboard-only and screenreader modes~
• Docs site QA
  • [ ] ~Added documentation~
  • [ ] ~Props have proper autodocs (using @default if default values are missing) and playground toggles~
  • [ ] ~Checked Code Sandbox works for any docs examples~
• Code quality checklist
  • [x] Added or updated jest ~and cypress tests~
  • [ ] ~Updated visual regression tests~
• Release checklist
  • [x] A changelog entry exists and is marked appropriately.
  • [x] If applicable, added the breaking change issue label (and filled out the breaking change checklist)
• Designer checklist
  • [x] If applicable, file an issue to update EUI's Figma library with any corresponding UI changes. (This is an internal repo, if you are external to Elastic, ask a maintainer to submit this request)