docs: Update README with the new release (#592)

**Reason for Change**:
<!-- What does this PR improve or fix in Kaito? Why is it needed? -->

**Requirements**

- [ ] added unit tests and e2e tests (if applicable).

**Issue Fixed**:
<!-- If this PR fixes GitHub issue 4321, add "Fixes #4321" to the next
line. -->

**Notes for Reviewers**:

README.md

@@ -7,7 +7,7 @@
 
 | ![notification](docs/img/bell.svg) What is NEW! |
 |-------------------------------------------------|
-| Latest Release: July 12th, 2024. Kaito v0.3.0.  |
+| Latest Release: Sep 9th, 2024. Kaito v0.3.1.    |
 | First Release: Nov 15th, 2023. Kaito v0.1.0.    |
 
 Kaito is an operator that automates the AI/ML model inference or tuning workload in a Kubernetes cluster.