Update `create_and_process_pipeline_spec` e2e spec to use new feature flag

What does this MR do?

Updates create_and_process_pipeline_spec end-to-end test to use the ci_drop_new_builds_when_ci_quota_exceeded feature flag.

Related to: #323274 (closed) and gitlab-com/gl-infra/production#4729 (closed)

Does this MR meet the acceptance criteria?

Conformity

• I have included a changelog entry, or it's not needed. (Does this MR need a changelog?)
• I have added/updated documentation, or it's not needed. (Is documentation required?)
• I have properly separated EE content from FOSS, or this MR is FOSS only. (Where should EE code go?)
• I have added information for database reviewers in the MR description, or it's not needed. (Does this MR have database related changes?)
• I have self-reviewed this MR per code review guidelines.
• This MR does not harm performance, or I have asked a reviewer to help assess the performance impact. (Merge request performance guidelines)
• I have followed the style guides.