Fix config for review-gcp-quotas-checks job

What does this MR do and why?

This MR changes a CI misconfiguration in review-gcp-quotas-checks job to fix a failing review-gcp-quotas-checks job #3405334666 in CI.

The problem was that before_script from review-gcp-quotas-checks is overriding the before_script from base-review-checks, which resulted that the job didn't run scripts/review_apps/gcp_cleanup.sh and setup_gcp_dependencies commands. We should remove before_script in review-gcp-quotas-checks to fix this.

Closes #384233 (closed)

How to set up and validate locally

After this change, review-gcp-quotas-checks job has the following before_script:

  before_script:
    - source scripts/review_apps/gcp_cleanup.sh
    - setup_gcp_dependencies
    - !reference [".use-kube-context", before_script]

Before	After ✅
https://gitlab.com/gitlab-org/gitlab/-/ci/editor?branch_name=master&tab=3	https://gitlab.com/gitlab-org/gitlab/-/ci/editor?branch_name=nh-fix-gcp-quotas-checks-script&tab=3

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