docs: readmeから後方互換性の注記を削除

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: AtsushiM

packages/eslint-plugin-smarthr/rules/best-practice-for-interactive-element/README.md

@@ -35,7 +35,7 @@
 #### smarthr-uiの対象要素
 
 - Accordion
-- AccordionPanel (後方互換性のために残す)
+- AccordionPanel
 - Anchor
 - Checkbox
 - Date