Bump rocm-docs-core from 0.20.0 to 0.21.0 in /docs/sphinx (#870)

* Bump rocm-docs-core from 0.20.0 to 0.21.0 in /docs/sphinx

Bumps [rocm-docs-core](https://github.com/RadeonOpenCompute/rocm-docs-core) from 0.20.0 to 0.21.0.
- [Release notes](https://github.com/RadeonOpenCompute/rocm-docs-core/releases)
- [Changelog](https://github.com/RadeonOpenCompute/rocm-docs-core/blob/develop/CHANGELOG.md)
- [Commits](https://github.com/RadeonOpenCompute/rocm-docs-core/compare/v0.20.0...v0.21.0)

---
updated-dependencies:
- dependency-name: rocm-docs-core
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

* replace noCI with ci:docs-only label

---------

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Sam Wu <sam.wu2@amd.com>

[ROCm/rccl commit: a433fcc726]

projects/rccl/.github/dependabot.yml

@@ -12,6 +12,6 @@ updates:
       interval: "daily"
     labels:
       - "dependencies"
-      - "noCI"
+      - "ci:docs-only"
     reviewers:
       - "samjwu"