fix(panel): Add native tooltip to close button. (#7434)

**Related Issue:** N/A

## Summary

fix(panel): Add native tooltip to close button.

- Modal uses a native tooltip for its close button
- Using a calcite-tooltip would be too much visual noise

packages/calcite-components/src/components/panel/panel.tsx

@@ -413,6 +413,7 @@ export class Panel
         icon={ICONS.close}
         onClick={close}
         text={text}
+        title={text}
         // eslint-disable-next-line react/jsx-sort-props
         ref={this.setCloseRef}
       />