[MM-61587]: Added appropriate ARIA attributes in the channel header (#29563)

* [MA-8]: Added appropriate ARIA attributes in the channel header

* [MA-8]: Review Fixes: Updated the aria-expanded ternary condition

* [MA-8]: Rebased with master and fixed e2e failing test

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Co-authored-by: Mattermost Build <build@mattermost.com>

e2e-tests/cypress/tests/integration/playbooks/channels/rhs/about_spec.js

@@ -90,7 +90,7 @@ describe('channels > rhs > header', {testIsolation: true}, () => {
             cy.get('#rhsContainer').findByTestId('rendered-run-name').should('be.visible').contains('new run name');
 
             // * make sure the channel name remains unchanged
-            cy.get('#channelHeaderInfo').contains(playbookRunName);
+            cy.get('#channelHeaderInfo').findByRole('heading').contains(playbookRunName);
         });
     });