Project release review instructions are out-of-date

- Mention of `integration-test.yaml` should be removed (it is automatically run by the Log4j CI pipeline for `release/`-prefixed branches)
- Reproducibility issues (due to `CI=true`)
- Instructions tell to merge, but this is not allowed anymore, we create a PR instead.
- Log4j's `pom.xml` has extra (site-related) variables that need to be updated

Start by locating the project’s release review instructions, then inspect the referenced integration-test.yaml and Log4j’s pom.xml. Verify the CI and CI=true reproducibility notes, the PR-based workflow, and the site-related variables; done means all four outdated instruction areas are corrected and the release guidance matches current practice.

Written by the indexing model from the issue text.