Amend release notes to make it clear that bzlmod support is only for Bazel 7+

### What happened?

https://github.com/bazel-contrib/rules_nodejs/commit/7a710426e108544b458e5ec888ad2f8eab8da12a introduces `use_repo_rule`, which was [introduced in Bazel 7](https://releases.bazel.build/7.0.0/release/index.html). In our case, bumping `rules_nodejs` from 6.3.0 to 6.7.5 therefore breaks compatibility with Bazel 6, even though Bazel 6 compatibility is claimed in [recent release notes](https://github.com/bazel-contrib/rules_nodejs/releases#release-v6.7.5). Is there some workaround which was envisioned, and/or is this a known issue?

### Version

- rules_nodejs version 6.7.5
- Bazel version 6.6

### How to reproduce

```shell
# MODULE.bazel
bazel_dep(name = "rules_nodejs", version = "6.7.5")
```

### Any other information?

_No response_

Start with the MODULE.bazel reproduction using rules_nodejs 6.7.5 and Bazel 6.6, then inspect commit 7a710426e108544b458e5ec888ad2f8eab8da12a and the v6.7.5 release notes. Determine whether use_repo_rule can work under Bazel 6 or whether the release's claimed compatibility is incorrect; done means documenting a workaround or confirming a compatibility fix.

Written by the indexing model from the issue text.