Remove RELEASE.md and consolidate into CONTRIBUTING.md

The release process documentation was duplicated. CONTRIBUTING.md
already contains more comprehensive release instructions, so remove
the redundant RELEASE.md and add the GitHub Actions workflow links
to CONTRIBUTING.md.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: kesmit13

CONTRIBUTING.md

@@ -261,16 +261,18 @@ Install from https://cli.github.com/ and run `gh auth login`.
    git commit -m "Prepare for v1.x.x release" && git push
    ```
 
-4. **Wait for CI tests to pass** on GitHub Actions
+4. **Wait for CI tests to pass** on GitHub Actions:
+   - [Coverage tests](https://github.com/singlestore-labs/singlestoredb-python/actions/workflows/coverage.yml)
+   - [Smoke tests](https://github.com/singlestore-labs/singlestoredb-python/actions/workflows/smoke-test.yml)
 
 5. **Create the GitHub release**:
    ```bash
    python resources/create_release.py
    ```
 
-6. **Verify PyPI publish** workflow completes successfully
-   (triggered automatically by the GitHub release). Check the
-   [PyPI package page](https://pypi.org/project/singlestoredb/) to confirm
+6. **Verify [PyPI publish](https://github.com/singlestore-labs/singlestoredb-python/actions/workflows/publish.yml)**
+   workflow completes successfully (triggered automatically by the GitHub release).
+   Check the [PyPI package page](https://pypi.org/project/singlestoredb/) to confirm
    the new version is available.
 
 ### Version File Locations