[Search:AppSearch:Engines:Relevance Tuning page]Heading levels announced together with button elements

[L1nBra]

Description
Buttons should be announced as button elements without headings.

Preconditions
Stateful App Search -> Engines -> Relevance Tuning page is opened.
Engine is added.
Use Screen Reader (NVDA).

Steps to reproduce

1.Navigate to the panel for a field name (below Manage fields) using only keyboard by pressing Tab key.
2.Observe screen reader.

NVDA speech viewer + UI elements

Actual Result

• Heading level is announced together with button element.

Expected Result

• Heading level is not announced for button element.

Meta Issue

Kibana Version: 8.17.0-SNAPSHOT

OS: Windows 11 Pro

Browser: Chrome Version 130.0.6723.70 (Official Build) (64-bit)

Screen reader: NVDA

WCAG or Vendor Guidance (optional)

• Understanding SC 4.1.2: Name, Role, Value (Level A)(https://www.w3.org/WAI/WCAG22/Understanding/name-role-value.html)

Related to: https://github.com/elastic/search-team/issues/8256

[elasticmachine]

Pinging @elastic/kibana-accessibility (Project:Accessibility)