[E2E] PROMOTE TO BLOCKING: distributed_reads_spec.rb

What does this MR do?

Promotes the following e2e tests to the blocking bucket:

1. Systems Gitaly distributed reads when a node is unhealthy does not read from the unhealthy node | Testcase | Spec metrics

This MR was created based on data from reliable e2e test report: #478428 (closed)

(This MR was automatically generated by gitlab_quality-test_tooling at 2024-08-12 02:06:17 UTC)