test: remove unused select2Nodes and fix flaky timeout

- Remove select2Nodes helper method from NodeOperationsHelper
- Replace usages with selectNodes(['CLIP Text Encode (Prompt)'])
- Increase flaky timeout in mobileBaseline test from 256ms to 5000ms

Amp-Thread-ID: https://ampcode.com/threads/T-019c15b9-efed-72eb-b092-1e92a11f44e3
Co-authored-by: Amp <amp@ampcode.com>

browser_tests/tests/rightClickMenu.spec.ts

@@ -34,7 +34,7 @@ test.describe(
     })
 
     test('Can convert to group node', async ({ comfyPage }) => {
-      await comfyPage.nodeOps.select2Nodes()
+      await comfyPage.nodeOps.selectNodes(['CLIP Text Encode (Prompt)'])
       await expect(comfyPage.canvas).toHaveScreenshot('selected-2-nodes.png')
       await comfyPage.canvasOps.rightClick()
       await comfyPage.clickContextMenuItem('Convert to Group Node (Deprecated)')
@@ -139,7 +139,7 @@ test.describe('Node Right Click Menu', { tag: ['@screenshot', '@ui'] }, () => {
   })
 
   test('Can pin/unpin selected nodes', async ({ comfyPage }) => {
-    await comfyPage.nodeOps.select2Nodes()
+    await comfyPage.nodeOps.selectNodes(['CLIP Text Encode (Prompt)'])
     await comfyPage.page.keyboard.down('Control')
     await comfyPage.rightClickEmptyLatentNode()
     await comfyPage.page.click('.litemenu-entry:has-text("Pin")')