chore: remove integ-runner steps from the yarn upgrade workflow (#33917)

### Issue # (if applicable)

Closes NA

### Reason for this change

`@aws-cdk/integ-runner` is removed from this repository with the [PR](#33835) and moved to `aws-cdk-cli` repository. Hence yarn upgrade workflow fails at the integ-runner build step as the package is no longer available in the repo.

### Description of changes

Remove the integ-runner build step as no longer applicable in the yarn upgrade workflow.

### Describe any new or updated permissions being added

NA

### Description of how you validated changes

* Ran `yarn install` and verified the integ-runner installed version using `npx integ-runner --version`

### Checklist
- [x] My code adheres to the [CONTRIBUTING GUIDE](https://github.com/aws/aws-cdk/blob/main/CONTRIBUTING.md) and [DESIGN GUIDELINES](https://github.com/aws/aws-cdk/blob/main/docs/DESIGN_GUIDELINES.md)

----

*By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license*

Author: godwingrs22

.github/workflows/yarn-upgrade.yml

@@ -39,10 +39,6 @@ jobs:
       - name: Install Tools
         run: |-
           npm -g install lerna npm-check-updates
-      - name: Build Integ Runner
-        run: |
-          export NODE_OPTIONS="--max-old-space-size=8196 --experimental-worker ${NODE_OPTIONS:-}"
-          npx lerna run build --scope @aws-cdk/integ-runner
       - name: List Mono-Repo Packages
         id: list-packages
         # These need to be ignored from the `ncu` runs!