fix(cdk-experimental/accordion): removes inert attribute from accordion trigger

Removes the inert attribute from accordion trigger to enable screen
readers to access the accordion trigger id and aria attributes to be
able to announce more helpful/informative screen reader messages to the
user.

Fixes b/438312273

Author: essjay05

src/cdk-experimental/accordion/accordion.ts

@@ -93,7 +93,6 @@ export class CdkAccordionPanel {
     '[attr.aria-expanded]': 'pattern.expanded()',
     '[attr.aria-controls]': 'pattern.controls()',
     '[attr.aria-disabled]': 'pattern.disabled()',
-    // '[attr.inert]': 'hardDisabled() ? true : null',
     '[attr.disabled]': 'hardDisabled() ? true : null',
     '[attr.tabindex]': 'pattern.tabindex()',
     '(keydown)': 'pattern.onKeydown($event)',