chore: remove auto-approve label from spec-update workflow (#33686)

### Description of changes
Remove the auto-approve label being added to the L1 CFN resource definition update PR. 

We want to manually review this PR before merging it in for any potential breaking changes. 

### 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)

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

Author: paulhcsun

.github/workflows/spec-update.yml

@@ -154,7 +154,7 @@ jobs:
           # Pull Request details
           title: "feat: update L1 CloudFormation resource definitions"
           body-path: ${{ runner.temp }}/PR.md
-          labels: contribution/core,dependencies,auto-approve,pr-linter/exempt-integ-test,pr-linter/exempt-readme,pr-linter/exempt-test
+          labels: contribution/core,dependencies,pr-linter/exempt-integ-test,pr-linter/exempt-readme,pr-linter/exempt-test
           team-reviewers: aws-cdk-team
           # Github prevents further Github actions to be run if the default Github token is used.
           # Instead use a privileged token here, so further GH actions can be triggered on this PR.