Bump rwkv from 0.3.1 to 0.4.2

Bumps [rwkv](https://github.com/BlinkDL/ChatRWKV) from 0.3.1 to 0.4.2.
- [Release notes](https://github.com/BlinkDL/ChatRWKV/releases)
- [Commits](https://github.com/BlinkDL/ChatRWKV/commits)

---
updated-dependencies:
- dependency-name: rwkv
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

requirements.txt

@@ -4,7 +4,7 @@ flexgen==0.1.7
 gradio==3.18.0
 numpy
 requests
-rwkv==0.3.1
+rwkv==0.4.2
 safetensors==0.3.0
 sentencepiece
 tqdm