chore(deps): update nginx:alpine docker digest to 756e5ce (#434)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

Dockerfile

@@ -41,7 +41,7 @@ RUN SECRET_KEY=dummy \
     python3 manage.py collectstatic --noinput
 
 # runtime nginx image
-FROM nginx:alpine@sha256:61e01287e546aac28a3f56839c136b31f590273f3b41187a36f46f6a03bbfe22 AS runtime-nginx
+FROM nginx:alpine@sha256:756e5cea3fcf99e6a63f97ab9196032fe8403070d2724388541ef917c62e13ba AS runtime-nginx
 
 COPY --from=builder /app/src/static_built /var/www/html/static
 COPY ./nginx/nginx.conf /etc/nginx/conf.d/default.conf