Update nginxinc/nginx-unprivileged Docker tag to v1.29.3 (#172)

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

Author: renovate[bot]

Earthfile

@@ -30,7 +30,7 @@ build:
     SAVE ARTIFACT site
 
 image:
-    FROM nginxinc/nginx-unprivileged:1.29.2-alpine
+    FROM nginxinc/nginx-unprivileged:1.29.3-alpine
     COPY fs /
     COPY --pass-args +build/site/ /usr/share/nginx/html/