Update nginxinc/nginx-unprivileged Docker tag to v1.27.3

This MR contains the following updates:

Package	Type	Update	Change
nginxinc/nginx-unprivileged	ironbank-docker	patch	1.27.2-bookworm -> 1.27.3-bookworm
nginxinc/nginx-unprivileged	stage	patch	1.27.2-bookworm -> 1.27.3-bookworm

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