Remove native title tooltip from StatCard help icon

[ousmaneo]

Hovering the help icon on a StatCard showed a small native "More info" tooltip that obscured the actual help popover.

StatCard passed triggerTitle="More info" to HoverForHelp, and OverlayTrigger renders that prop as both aria-label and a native title attribute. This removes the prop. OverlayTrigger falls back to the card label for aria-label, so the icon keeps an accessible name.

part of https://github.com/Graylog2/graylog-plugin-enterprise/issues/15615

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Refactoring (non-breaking change)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have requested a documentation update.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.