[CI] Prepare for PIP-156 (#15264) build changes by dropping some required checks (#15496)
[CI] Prepare for PIP-156 (#15264) build changes by dropping some required checks (#15496)

- PR #15264 makes changes to the build jobs and it's necessary to drop the required
  checks `CI - Unit - Brokers - JDK 8` and `CI - Integration - Shade` before the
  PR can be merged`
yahoo/pulsar,massakam/pulsar,merlimat/pulsar,massakam/pulsar,yahoo/pulsar,merlimat/pulsar,massakam/pulsar,yahoo/pulsar,merlimat/pulsar,merlimat/pulsar,massakam/pulsar,yahoo/pulsar,yahoo/pulsar,massakam/pulsar,merlimat/pulsar,massakam/pulsar,yahoo/pulsar,merlimat/pulsar