Fixed Add Channel_test_cases (#22768)

* Fixed Add Channel_test_cases

* fixed more test cases

* fixed lint

e2e-tests/cypress/tests/integration/channels/channel_sidebar/category_sorting_1_spec.ts

@@ -140,7 +140,7 @@ function createCategoryFromSidebarMenu() {
     const categoryName = `category-${getRandomId()}`;
 
     // # Click on the sidebar menu dropdown
-    cy.findByLabelText('Add Channel Dropdown').click();
+    cy.uiGetLHSAddChannelButton().click();
 
     // # Click on create category link
     cy.findByText('Create New Category').should('be.visible').click();

e2e-tests/cypress/tests/integration/channels/channel_sidebar/category_sorting_spec.ts

@@ -23,7 +23,7 @@ describe('Category sorting', () => {
 
     it('MM-T3916 Create Category character limit', () => {
         // # Click on the sidebar menu dropdown
-        cy.findByLabelText('Add Channel Dropdown').click();
+        cy.uiGetLHSAddChannelButton().click();
 
         // # Click on create category link
         cy.findByText('Create New Category').should('be.visible').click();

e2e-tests/cypress/tests/integration/channels/channel_sidebar/custom_categories_spec.ts

@@ -90,7 +90,7 @@ function createCategoryFromSidebarMenu() {
     const categoryName = `category-${getRandomId()}`;
 
     // # Click on the sidebar menu dropdown
-    cy.findByLabelText('Add Channel Dropdown').click();
+    cy.uiGetLHSAddChannelButton().click();
 
     // # Click on create category link
     cy.findByText('Create New Category').should('be.visible').click();

e2e-tests/cypress/tests/integration/channels/channel_sidebar/new_channel_dropdown_spec.ts

@@ -62,7 +62,7 @@ describe('Channel sidebar', () => {
         cy.url().should('include', `/${teamName}/channels/town-square`);
 
         // # Click the New Channel Dropdown button
-        cy.get('.AddChannelDropdown_dropdownButton').should('be.visible').click();
+        cy.uiGetLHSAddChannelButton().should('be.visible').click();
 
         // # Click the Browse Channels dropdown item
         cy.get('.AddChannelDropdown .MenuItem:contains(Browse Channels) button').should('be.visible').click();