[deps] Bump nginx in /images/openwisp_nginx

Bumps nginx from 1.23.4-alpine to 1.27.0-alpine.

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

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

images/openwisp_nginx/Dockerfile

@@ -1,4 +1,4 @@
-FROM nginx:1.23.4-alpine
+FROM nginx:1.27.0-alpine
 
 RUN apk add --update --no-cache \
             openssl~=3.0.14-r0 \