repo: Release v1.31.4

**Summary of changes**:

- Minor bug fixes

**Docker images**:
    https://hub.docker.com/r/envoyproxy/envoy/tags?page=1&name=v1.31.4
**Docs**:
    https://www.envoyproxy.io/docs/envoy/v1.31.4/
**Release notes**:
    https://www.envoyproxy.io/docs/envoy/v1.31.4/version_history/v1.31/v1.31.4
**Full changelog**:
    https://github.com/envoyproxy/envoy/compare/v1.31.3...v1.31.4



Signed-off-by: Ryan Northey <ryan@synca.io>