[MM-61637]: Add accessible name to the expand RHS button in RHS header (#29783)

* [MA-48]: Add aria-label

* [MA-48]: Update snapshots

* [MA-48]: Fix E2E tests

e2e-tests/cypress/tests/integration/channels/accessibility/accessibility_buttons_spec.js

@@ -35,11 +35,7 @@ describe('Verify Accessibility Support in different Buttons', () => {
             within(() => {
                 // * Verify accessibility support in Sidebar Expand and Shrink icon
                 cy.get('button.sidebar--right__expand').
-                    should('have.attr', 'aria-label', 'Expand').
-                    within(() => {
-                        cy.get('.icon-arrow-expand').should('have.attr', 'aria-label', 'Expand Sidebar Icon');
-                        cy.get('.icon-arrow-collapse').should('have.attr', 'aria-label', 'Collapse Sidebar Icon');
-                    });
+                    should('have.attr', 'aria-label', 'Expand Sidebar Icon');
 
                 // * Verify accessibility support in Close icon
                 cy.get('#rhsCloseButton').

e2e-tests/cypress/tests/support/ui/sidebar_right.js

@@ -19,7 +19,7 @@ Cypress.Commands.add('uiCloseRHS', () => {
 });
 
 Cypress.Commands.add('uiExpandRHS', () => {
-    cy.findByLabelText('Expand').click();
+    cy.findByLabelText('Expand Sidebar Icon').click();
 });
 
 Cypress.Commands.add('isExpanded', {prevSubject: true}, (subject) => {