test: [M3-10628] - Fix Cypress test failures after LKE-E Post LA flag was toggled on

[mjac0bs]

Description 📝

We started seeing test failures since we turned the LKE-Enterprise postLa flag on in prod yesterday. Based on the screenshot, a couple of current tests haven't accounted for the change to the Node Pool plans table, which no longer has an enhanced number input increment/decrement button. That has been moved inside the Configure Pool drawer.

Changes 🔄

• Update plan-selection.spec.ts to remove the check for the disabled increment/decrement buttons. Just a disabled Configure Pool button is visible now.
• Update smoke-lke-standard-create.spec.ts to use the new LKE helper functions and correctly reference the Configure Pool button, rather than attempt to click the enhanced number input buttons in the plan row.

Scope 🚢

Upon production release, changes in this PR will be visible to:

• All customers
• Some customers (e.g. in Beta or Limited Availability)
• No customers / Not applicable

Target release date 🗓️

9/23 - let's please get this in so that we don't have to deal with these test failures in the release

Preview 📷

Before	After

How to test 🧪

Reproduction steps

(How to reproduce the issue, if applicable)

• Check out develop and run these tests, or check the notifications Slack channel and observe the recent test failures

Verification steps

(How to verify changes)

• Watch CI or check out this branch locally and:

pnpm cy:run -s "cypress/e2e/core/linodes/plan-selection.spec.ts,cypress/e2e/core/kubernetes/smoke-lke-standard-create.spec.ts"

Author Checklists

As an Author, to speed up the review process, I considered 🤔

👀 Doing a self review
❔ Our contribution guidelines
🤏 Splitting feature into small PRs
➕ Adding a changeset
🧪 Providing/improving test coverage
🔐 Removing all sensitive information from the code and PR description
🚩 Using a feature flag to protect the release
👣 Providing comprehensive reproduction steps
📑 Providing or updating our documentation
🕛 Scheduling a pair reviewing session
📱 Providing mobile support
♿ Providing accessibility support

• I have read and considered all applicable items listed above.

As an Author, before moving this PR from Draft to Open, I confirmed ✅

• All tests and CI checks are passing
• TypeScript compilation succeeded without errors
• Code passes all linting rules

[jdamore-linode]

Thanks @mjac0bs! Confirmed they're passing locally

[hana-akamai]

Confirmed that tests pass locally! 🚢