chore(deps): bump coder/coder from v2.18.3 to v2.18.4 in /render

Bumps [coder/coder](https://github.com/coder/coder) from v2.18.3 to v2.18.4.
- [Release notes](https://github.com/coder/coder/releases)
- [Changelog](https://github.com/coder/coder/blob/main/release.key)
- [Commits](coder/coder@v2.18.3...v2.18.4)

---
updated-dependencies:
- dependency-name: coder/coder
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>

render/Dockerfile

@@ -1,4 +1,4 @@
-FROM ghcr.io/coder/coder:v2.18.3
+FROM ghcr.io/coder/coder:v2.18.4
 ARG RENDER_EXTERNAL_URL
 ENV CODER_HTTP_ADDRESS=0.0.0.0:3000
 ENV CODER_ACCESS_URL=${RENDER_EXTERNAL_URL}